Enhanced remote astronomical archive system based on the file-level Unlimited Sliding-Window technique

Data archiving is one of the most critical issues for modern astronomical observations. With the development of a new generation of radio telescopes, the transfer and archiving of massive remote data have become urgent problems to be solved. Herein, we present a practical and robust file-level flow-control approach, called the Unlimited Sliding-Window (USW), by referring to the classic flow-control method in the TCP protocol. Based on the USW and the Next Generation Archive System (NGAS) developed for the Murchison Widefield Array telescope, we further implemented an enhanced archive system (ENGAS) using ZeroMQ middleware. The ENGAS substantially improves the transfer performance and ensures the integrity of transferred files. In the tests, the ENGAS is approximately three to twelve times faster than the NGAS and can fully utilize the bandwidth of network links. Thus, for archiving radio observation data, the ENGAS reduces the communication time, improves the bandwidth utilization, and solves the remote synchronous archiving of data from observatories such as Mingantu spectral radioheliograph. It also provides a better reference for the future construction of the Square Kilometer Array (SKA) Science Regional Center.

Energy estimation of high-energy particles associated with the SS 433/W 50 system through radio observation at 1.4 GHz

The radio nebula W 50 is a unique object interacting with the jets of the microquasar SS 433. The SS 433/W 50 system is a good target for investigating the energy of cosmic-ray particles accelerated by galactic jets. We report observations of the radio nebula W 50 conducted with the National Science Foundation’s Karl G. Jansky Very Large Array in the L band (1.0–2.0 GHz). We investigate the secular change of W 50 on the basis of the observations in 1984, 1996, and 2017, and find that most of its structures were stable for 33 yr. We revise the upper-limit velocity of the eastern terminal filament by half to 0.023 c, assuming a distance of 5.5 kpc. We also analyze observational data from the Arecibo Observatory 305 m telescope and identify the H i cavity around W 50 in the velocity range 33.77–55.85 km s−1. From this result, we estimate the maximum energy of the cosmic-ray protons accelerated by the jet terminal region to be above 1015.5 eV. We also use the luminosity of the gamma-rays in the range 0.5–10 GeV to estimate the total energy of accelerated protons below 5.2 × 1048 erg.

Post-Newtonian Kozai–Lidov mechanism and its effect on cumulative shift of periastron time of binary pulsar

ABSTRACT We study the Kozai–Lidov mechanism in a hierarchical triple system in detail by the direct integration of the first-order post-Newtonian equations of motion. We analyse a variety of models with a pulsar to evaluate the cumulative shift of the periastron time of a binary pulsar caused by the gravitational wave emission in a hierarchical triple system with Kozai–Lidov mechanism. We compare our results with those by the double-averaging method. The deviation in the eccentricity, even if small, is important in the evaluation of the emission of the gravitational waves. We also calculate the cumulative shift of the periastron time by using obtained osculating orbital elements. If Kozai–Lidov oscillations occur, the cumulative shift curve will bend differently from that of the isolated binary. If such a bending is detected through the radio observation, it will be the first indirect observation of gravitational waves from a triple system.

4-years lightning hunt in Venus

<p class="p1"><span class="s1"><span class="Apple-converted-space">  </span>For more than 3 decades the existence of lightning discharge in Venus has been controversial, which might be caused by insufficient observational methods optimized for such purpose. There had been no satellite payload intentionally designed for the detection of lightning phenomena using radio waves or optical sensors. LAC, lightning and airglow camera, onboard Akatsuki spacecraft developed by Hokkaido University together with JAXA, is the first sensor made for the lightning optical flash detection in planets other than the Earth. A unique performance of LAC compared to other equipment used in the previous exploration of Venus is the high-speed sampling rate at 20 kHz with 32 pixels of Avalanche Photo Diode (APD) matrix, enabling us to distinguish the natural optical lightning flash from other pulsing noises, including artificial electrical noise and cosmic rays. We selected OI 777 nm line for lightning detection, which is expected to be the most prominent emission in the CO2-dominant atmosphere based on the laboratory discharge experiments carried out by some researchers. We have been conducting lightning hunt since October 2016 with LAC onboard Akatsuki, selecting triggering parameter sets optimized for the light curve similar to the normal lightning and also for sprite type in the Earth, which has a slower variation of optical intensity. The total coverage of the LAC lightning hunt became approximately 100 [million km2-hr], meaning 86 percent detectability of previous results with a ground-based telescope by Hansell et al. (1995).<span class="Apple-converted-space">  </span>Here we report the update of the detailed examination of recorded data by LAC for these almost 4 years and discuss their possible interpretation, considering all kinds of candidates of optical and other sources. Also, the future observation strategy including ground observation with a high-speed photometer installed at the ground telescope and radio observation will be introduced. </span></p>

Where is the western part of the Galactic Center Lobe located really?

The Galactic Center Lobe (GCL) is a peculiar object widely protruding from the Galactic plane toward the positive Galactic latitude, which had been found toward the Galactic Center (GC) in the early days of the radio observation. The peculiar shape has suggested a relation with historical events, star burst, large explosion, and so on in the GC. However, the issue of whether the GCL is a single large structure located in the GC region is not yet settled conclusively. In the previous observations, the silhouette against the low-frequency emission was found in the western part of the GCL (WPGCL); this suggests that the part is located in front of the GC region. On the other hand, the Local Standard of Rest (LSR) velocity of the radio recombination line toward it was found to be as low as 0 km s−1. However, these observations cannot determine the exact position on the line-of-sight. There is still another possibility that it is in the near-side area of the GC region. In this analysis, we compare these results with the visual extinction map toward the GC. We found that the distribution of the visual extinction larger than 4 mag clearly corresponds to the silhouette of the WPGCL. The WPGCL must be located at most within a few kpc from us and not in the GC region. This would be a giant H ii region in the Galactic disk.

The MAVERIC survey: a hidden pulsar and a black hole candidate in ATCA radio imaging of the globular cluster NGC 6397

ABSTRACT Using a 16.2-h radio observation by the Australia Telescope Compact Array and archival Chandra data, we found >5σ radio counterparts to four known and three new X-ray sources within the half-light radius (rh) of the Galactic globular cluster NGC 6397. The previously suggested millisecond pulsar (MSP) candidate, U18, is a steep-spectrum (Sν ∝ να; $\alpha =-2.0^{+0.4}_{-0.5}$) radio source with a 5.5-GHz flux density of 54.7 ± 4.3 $\mu \mathrm{ Jy}$. We argue that U18 is most likely a ‘hidden’ MSP that is continuously hidden by plasma shocked at the collision between the winds from the pulsar and companion star. The non-detection of radio pulsations so far is probably the result of enhanced scattering in this shocked wind. On the other hand, we observed the 5.5-GHz flux of the known MSP PSR J1740−5340 (U12) to decrease by a factor of >2.8 during epochs of 1.4-GHz eclipse, indicating that the radio flux is absorbed in its shocked wind. If U18 is indeed a pulsar whose pulsations are scattered, we note the contrast with U12’s flux decreases in eclipse, which argues for two different eclipse mechanisms at the same radio frequency. In addition to U12 and U18, we also found radio associations for five other Chandra X-ray sources, four of which are likely background galaxies. The last, U97, which shows strong H α variability, is mysterious; it may be either a quiescent black hole low-mass X-ray binary or something more unusual.