23 research outputs found
Meter- to Millimeter Emission from Cool Stellar Systems : Latest Results, Synergies Across the Spectrum, and Outlook for the Next Decade
Splinter session summary, to appear in the proceedings of the 20th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun (ed. S. J. Wolk)Radio observations of cool stellar systems provide unique information on their magnetic fields, high-energy processes, and chemistry. Buoyed by powerful new instruments (e.g. ALMA, JVLA, LOFAR), advances in related fields (e.g., the Gaia astrometric revolution), and above all a renewed interest in the relevant stellar astrophysics, stellar radio astronomy is experiencing a renaissance. In this splinter session, participants took stock of the present state of stellar radio astronomy to chart a course for the field's future
Serendipitous Discovery of PSR J1431-6328 as a Highly-Polarized Point Source with the Australian SKA Pathfinder
We identified a highly-polarized, steep-spectrum radio source in a deep image
with the Australian Square Kilometre Array Pathfinder (ASKAP) telescope at 888
MHz. After considering and rejecting a stellar origin for this source, we
discovered a new millisecond pulsar (MSP) using observations from the Parkes
radio telescope. This pulsar has period 2.77 ms and dispersion measure 228.27
pc/cm**3. Although this pulsar does not yet appear to be particularly
remarkable, the short spin period, wide profile and high dispersion measure do
make it relatively hard to discover through traditional blind periodicity
searches. Over the course of several weeks we see changes in the barycentric
period of this pulsar that are consistent with orbital motion in a binary
system, but the properties of any binary need to be confirmed by further
observations. While even a deep ASKAP survey may not identify large numbers of
new MSPs compared to the existing population, it would be competitive with
existing all-sky surveys and could discover interesting new MSPs at high
Galactic latitude without the need for computationally-expensive all-sky
periodicity searches.Comment: ApJ, in pres
A pilot ASKAP survey for radio transients towards the Galactic Centre
We present the results of a radio transient and polarisation survey towards
the Galactic Centre, conducted as part of the Australian Square Kilometre Array
Pathfinder Variables and Slow Transients pilot survey. The survey region
consisted of five fields covering (, ). Each field was observed
for 12\,minutes, with between 7 and 9 repeats on cadences of between one day
and four months. We detected eight highly variable sources and seven highly
circularly-polarised sources (14 unique sources in total). Seven of these
sources are known pulsars including the rotating radio transient
PSR~J1739--2521 and the eclipsing pulsar PSR~J1723--2837. One of them is a low
mass X-ray binary, 4U 1758--25. Three of them are coincident with optical or
infrared sources and are likely to be stars. The remaining three may be related
to the class of Galactic Centre Radio Transients (including a highly likely
one, VAST~J173608.2--321634, that has been reported previously), although this
class is not yet understood. In the coming years, we expect to detect 40
bursts from this kind of source with the proposed four-year VAST survey if the
distribution of the source is isotropic over the Galactic fields.Comment: 17 pages, 13 figures, Accepted for publication in MNRA
SPARKESX: Single-dish PARKES data sets for finding the uneXpected -- A data challenge
New classes of astronomical objects are often discovered serendipitously. The
enormous data volumes produced by recent high-time resolution, radio-telescope
surveys imply that efficient algorithms are required for a discovery. Such
algorithms are usually tuned to detect specific, known sources. Existing data
sets therefore likely contain unknown astronomical sources, which will remain
undetected unless algorithms are developed that can detect a more diverse range
of signals. We present the Single-dish PARKES data challenge for finding the
uneXpected (SPARKESX), a compilation of real and simulated high-time resolution
observations. SPARKESX comprises three mock surveys from the Parkes "Murriyang"
radio telescope. A broad selection of simulated and injected expected signals
(such as pulsars, fast radio bursts), poorly characterised signals (plausible
flare star signatures) and unknown unknowns are generated for each survey. The
goal of this challenge is to aid in the development of new algorithms that can
detect a wide-range of source types. We show how successful a typical pipeline
based on the standard pulsar search software, PRESTO, is at finding the
injected signals. The dataset is publicly available at
https://doi.org/10.25919/fd4f-0g20.Comment: Accepted for publication in MNRAS. 18 pages, 8 figures, 4 tabl
Discovery of a young, highly scattered pulsar PSR J1032-5804 with the Australian SKA Pathfinder
We report the discovery of a young, highly scattered pulsar in a search for
highly circularly polarized radio sources as part of the Australian Square
Kilometre Array Pathfinder (ASKAP) Variables and Slow Transients (VAST) survey.
In follow-up observations with Murriyang/Parkes, we identified PSR J1032-5804
and measured a period of 78.7 ms, dispersion measure (DM) of 8194 pc
cm, rotation measure of -20001 rad m, and a characteristic
age of 34.6 kyr. We found a pulse scattering timescale at 3 GHz of ~22 ms,
implying a timescale at 1 GHz of ~3845 ms, which is the third most scattered
pulsar known and explains its non-detection in previous pulsar surveys. We
discuss the identification of a possible pulsar wind nebula and supernova
remnant in the pulsar's local environment by analyzing the pulsar spectral
energy distribution and the surrounding extended emission from multiwavelength
images. Our result highlights the possibility of identifying extremely
scattered pulsars from radio continuum images. Ongoing and future large-scale
radio continuum surveys will offer us an unprecedented opportunity to find more
extreme pulsars (e.g., highly scattered, highly intermittent, highly
accelerated), which will enhance our understanding of the characteristics of
pulsars and the interstellar medium.Comment: 15 pages, 10 figures, 2 tables. Accepted for publication in Ap
Induced pluripotent stem cell-derived cells model brain microvascular endothelial cell glucose metabolism
Glucose transport from the blood into the brain is tightly regulated by brain microvascular endothelial cells (BMEC), which also use glucose as their primary energy source. To study how BMEC glucose transport contributes to cerebral glucose hypometabolism in diseases such as Alzheimer’s disease, it is essential to understand how these cells metabolize glucose. Human primary BMEC (hpBMEC) can be used for BMEC metabolism studies; however, they have poor barrier function and may not recapitulate in vivo BMEC function. iPSC-derived BMEC-like cells (hiBMEC) are readily available and have good barrier function but may have an underlying epithelial signature. In this study, we examined differences between hpBMEC and hiBMEC glucose metabolism using a combination of dynamic metabolic measurements, metabolic mass spectrometry, RNA sequencing, and Western blots. hiBMEC had decreased glycolytic flux relative to hpBMEC, and the overall metabolomes and metabolic enzyme levels were different between the two cell types. However, hpBMEC and hiBMEC had similar glucose metabolism, including nearly identical glucose labeled fractions of glycolytic and TCA cycle metabolites. Treatment with astrocyte conditioned media and high glucose increased glycolysis in both hpBMEC and hiBMEC, though hpBMEC decreased glycolysis in response to fluvastatin while hiBMEC did not. Together, these results suggest that hiBMEC can be used to model cerebral vascular glucose metabolism, which expands their use beyond barrier models.https://doi.org/10.1186/s12987-022-00395-
Radio Variable and Transient Sources on Minute Timescales in the ASKAP Pilot Surveys
We present results from a radio survey for variable and transient sources on
15-min timescales, using the Australian SKA Pathfinder (ASKAP) pilot surveys.
The pilot surveys consist of 505 h of observations conducted at around 1 GHz
observing frequency, with a total sky coverage of 1476 deg. Each
observation was tracked for approximately 8-10h, with a typical rms sensitivity
of 30 jy/beam and an angular resolution of 12 arcsec. The
variability search was conducted within each 8-10h observation on a 15-min
timescale. We detected 38 variable and transient sources. Seven of them are
known pulsars, including an eclipsing millisecond pulsar, PSR J20395617.
Another eight sources are stars, only one of which has been previously
identified as a radio star. For the remaining 23 objects, 22 are associated
with active galactic nuclei or galaxies (including the five intra-hour
variables that have been reported previously), and their variations are caused
by discrete, local plasma screens. The remaining source has no multi-wavelength
counterparts and is therefore yet to be identified. This is the first
large-scale radio survey for variables and transient sources on minute
timescales at a sub-mJy sensitivity level. We expect to discover 1 highly
variable source per day using the same technique on the full ASKAP surveys.Comment: 20 pages, 11 figures; accepted for publication in MNRA