B0943+10: low-frequency study of subpulse periodicity in the Bright mode with LOFAR

We use broadband sensitive LOFAR observations in the 25-80 MHz frequency range to study the single-pulse emission properties of the mode-switching pulsar B0943+10. We review the derivation of magnetospheric geometry, originally based on low-frequency radio data, and show that the geometry is less constrained than previously thought. This may be used to help explain the large fractional amplitudes of the observed thermal X-ray pulsations from the polar cap, which contradict the almost aligned rotator model of PSR B0943+10. We analyse the properties of drifting subpulses in the Bright mode and report on the minutes-long variations of the drift period. We searched for the periodic amplitude modulation of drifting subpulses, which is a vital argument for constraining several important system parameters: the degree of aliasing, the orientation of the line-of-sight vector with respect to magnetic and spin axes, the angular velocity of the carousel, and thus, the gradient of the accelerating potential in the polar gap. The periodic amplitude modulation was not detected, indicating that it may be a rare or narrow-band phenomenon. Based on our non-detection and review of available literature, we chose to leave the aliasing order unconstrained and derived the number of sparks under different assumptions about the aliasing order and geometry angles. Contrary to the previous findings, we did not find a large (of the order of 10%) gradual variation of the separation between subpulses throughout Bright mode. We speculate that this large variation may be due to the incorrect accounting for the curvature of the line of sight within the on-pulse window. Finally, we report on the frequency-dependent drift phase delay, which is similar to the delay reported previously for PSR B0809+74. We provide a quantitative explanation of the observed frequency-dependent drift phase delay within the carousel model.Comment: updated to match the accepted version (A&A); added polarisation discussion and language correction

LOFAR observations of the mode-switching pulsar B0943+10

PSR B0943+10 is an old non-recycled pulsar which for decades has been mostly known for its rapid and spontaneous radio mode switching. Recently, Hermsen et al. (2013) discovered correlated changes in the thermal X-ray emission from the polar cap, thus demonstrating that radio modes are not just a product of the local changes in the radio emission region, but a sign of some global magnetospheric transformation. At about the same time, owing to the commissioning of the new generation of low-frequency radio arrays, the broadband observations at the lowest edge of ionospheric transparency window became available. At these radio frequencies profile morphology and the single-pulse properties of PSR B0943+10's emission become very dynamic, providing details not only about the emission itself, but also about the conditions in the polar gap. Here, I will present the recent results of the LOFAR observations of PSR B0943+10 and discuss their contribution to the multiwavelength picture.Comment: Proceedings of IAU Symposium 337 - 50 Years of Pulsars. Text is based on Bilous 2017 (arXiv:1710.05621) and Bilous et al. 2014 (arXiv:1408.5272

A uniform search for thermonuclear burst oscillations in the RXTE legacy dataset

We describe a blind uniform search for thermonuclear burst oscillations (TBOs) in the majority of Type-I bursts observed by RXTE (2118 bursts from 57 neutron stars). We examined 2-2002 Hz power spectra from the Fourier transform in sliding 0.5-2 s windows, using fine-binned light curves in 2-60 keV energy range. The significance of the oscillation candidates was assessed by simulations which took into account light curve variations, dead time and sliding time windows. Some of our sources exhibited multi-frequency variability below approximately 15 Hz that cannot be readily removed with light-curve modeling and may have an astrophysical (non-TBO) nature. Overall, we found that the number and strength of potential candidates depends strongly on the parameters of the search. We found candidates from all previously known RXTE TBO sources, with pulsations that had been detected at similar frequencies in multiple independent time windows, and discovered TBOs from SAX J1810.8-2658. We could not confirm most previously-reported tentative TBO detections or identify any obvious candidates just below the detection threshold at similar frequencies in multiple bursts. We computed fractional amplitudes of all TBO candidates and placed upper limits on non-detections. Finally, for a few sources we noted small excess of candidates with powers comparable to fainter TBOs, but appearing in single independent time bins at random frequencies. At least some of these candidates may be noise spikes that appear interesting due to selection effects. The potential presence of such candidates calls for extra caution if claiming single-bin TBO detections.Comment: Replaced to match the accepted version. Accepted to ApJS after numerous minor correction

The Discovery of Transitive Phenomenon in the Radio Emission of the mode-switcher PSR B0943+10

B0943+10 is known to switch between two distinct, hours-long modes of radio emission, Bright (B) and Quiet (Q). Up to now the switches in both directions were believed to occur instantly (on the scale of a spin period). We have found a transitive process around the Q-to-B-mode switch, which consists of two additional short-lived modes, each with distinct average profiles and subpulse drift rates. Based on observations at low radio frequencies, we examine the properties of these transitive modes and discuss their implications in the framework of the traditional carousel model of drifting subpulses.Comment: submitted to A&

A Giant Sample of Giant Pulses from the Crab Pulsar

We observed the Crab pulsar with the 43-m telescope in Green Bank, WV over a timespan of 15 months. In total we obtained 100 hours of data at 1.2 GHz and seven hours at 330 MHz, resulting in a sample of about 95000 giant pulses (GPs). This is the largest sample, to date, of GPs from the Crab pulsar taken with the same telescope and backend and analyzed as one data set. We calculated power-law fits to amplitude distributions for main pulse (MP) and interpulse (IP) GPs, resulting in indices in the range of 2.1-3.1 for MP GPs at 1.2 GHz and in the range of 2.5-3.0 and 2.4-3.1 for MP and IP GPs at 330 MHz. We also correlated the GPs at 1.2 GHz with GPs from the Robert C. Byrd Green Bank Telescope (GBT), which were obtained simultaneously at a higher frequency (8.9 GHz) over a span of 26 hours. In total, 7933 GPs from the 43-m telescope at 1.2 GHz and 39900 GPs from the GBT were recorded during these contemporaneous observations. At 1.2 GHz, 236 (3%) MP GPs and 23 (5%) IP GPs were detected at 8.9 GHz, both with zero chance probability. Another 15 (4%) low-frequency IP GPs were detected within one spin period of high-frequency IP GPs, with a chance probability of 9%. This indicates that the emission processes at high and low radio frequencies are related, despite significant pulse profile shape differences. The 43-m GPs were also correlated with Fermi gamma-ray photons to see if increased pair production in the magnetosphere is the mechanism responsible for GP emission. A total of 92022 GPs and 393 gamma-ray photons were used in this correlation analysis. No significant correlations were found between GPs and gamma-ray photons. This indicates that increased pair production in the magnetosphere is likely not the dominant cause of GPs. Possible methods of GP production may be increased coherence of synchrotron emission or changes in beaming direction.Comment: 33 pages, 10 figures, 6 tables, accepted for publication in Ap

Розробка методу сегментування замаскованої військової техніки на зображеннях з космічних систем спостереження з використанням генетичного алгоритму

The object of this research is the process of segmentation of camouflaged military equipment in images from space surveillance systems. The method of segmentation of camouflaged military equipment in images from space surveillance systems has been improved using a genetic algorithm. Unlike known methods, the method of segmentation of camouflaged military equipment using a genetic algorithm involves the following: – highlighting brightness channels in the Red-Green-Blue color space; – the use of a genetic algorithm in the image in each channel of brightness of the RGB color space; – image segmentation is reduced to the formation of generations and populations of chromosomes, the calculation of the objective function, selection, crossing, mutation, and decoding of chromosomes in each brightness channel of the Red-Green-Blue color space. Experimental studies were conducted on the segmentation of camouflaged military equipment using a genetic algorithm. It is established that the improved method of segmentation using a genetic algorithm makes it possible to segment images from space surveillance systems. A comparison of the quality of segmentation was carried out. It is established that the improved method of segmentation using a genetic algorithm reduces segmentation errors in the following way: – compared to the known k-means method, by an average of 15 % of errors of the first kind and an average of 7 % of errors of the second kind; – compared to the method of segmentation based on the algorithm of swarm of particles, by an average of 3.8 % of errors of the first kind and an average of 2.9 % of errors of the second kind. The improved segmentation method using a genetic algorithm can be implemented in software and hardware imaging systems from space surveillance systemsОб’єктом дослідження є процес сегментування замаскованої військової техніки на зображеннях з космічних систем спостереження. Удосконалено метод сегментування замаскованої військової техніки на зображеннях з космічних систем спостереження з використанням генетичного алгоритму. На відміну від відомих, метод сегментування замаскованої військової техніки з використанням генетичного алгоритму передбачає: – виділення каналів яскравості в кольоровому просторі Red-Green-Blue; – використання генетичного алгоритму на зображенні в кожному каналі яскравості кольорового простору RGB; – сегментування зображення зведено до формування поколінь та популяцій хромосом, обчислення цільової функції, селекції, схрещування, мутації та декодування хромосом в кожному каналі яскравості кольорового простору Red-Green-Blue. Проведені експериментальні дослідження щодо сегментування замаскованої військової техніки з використанням генетичного алгоритму. Встановлено, що удосконалений метод сегментування з використанням генетичного алгоритму дозволяє проводити сегментування зображень з космічних систем спостереження. Проведено порівняння якості сегментування. Встановлено, що удосконалений метод сегментування з використанням генетичного алгоритму забезпечує зниження помилок сегментування: – у порівнянні з відомим методом k-means в середньому на 15 % помилок І роду та в середньому на 7 % помилок ІI роду; – у порівнянні з методом сегментування на основі алгоритму рою частинок в середньому на 3,8 % помилок І роду та в середньому на 2,9 % помилок ІІ роду. Удосконалений метод сегментування з використанням генетичного алгоритму може бути реалізований у програмно-апаратних комплексах обробки зображень з космічних систем спостереженн

Varietal research on fresh and fresh frozen cherry fruit grown under the conditions of the Southern Steppe of Ukraine

UK: Проведено біохімічну оцінку 6 сортозразків вишні в свіжому стані (Шалунья, Нарядна, Сіянець Туровцевої, Експромт, Ерудітка, Відродження) за показниками: сума цукрів, кислота титрована, вітамін С, сума БАР. У заморожених сортозразках визначено параметр – величина втрати соку. RU: Проведена биохимическая оценка 6 сортообразцов вишни в свежем виде (Шалунья, Нарядная, Сеянец Туровцевой, Экспромт, Эрудитка, Возрождение) по показателям: сумма сахаров, кислота титрованная, витамин С, сумма БАВ. В замороженных сортообразцах определен параметр – величина потери сока. EN: The physical and biochemical assessment of fresh fruits of samples of 6 varieties of cherries was conducted (Shalunia, Nariadna, SiianetsTurovtsevoi, Ekspromt, Eruditka, Vidrodzhennia) by using the indicators: amount of sugars, titrated acid, vitamin C, the amount of biologically active substances (BAS). Such a parameter as amount of juice loss has been determined in the frozen varieties

Translating HbA1c measurements into estimated average glucose values in pregnant women with diabetes

Aims/hypothesis This study aimed to examine the relationship between average glucose levels, assessed by continuous glucose monitoring (CGM), and HbA1c levels in pregnant women with diabetes to determine whether calculations of standard estimated average glucose (eAG) levels from HbA1c measurements are applicable to pregnant women with diabetes. Methods CGM data from 117 pregnant women (89 women with type 1 diabetes; 28 women with type 2 diabetes) were analysed. Average glucose levels were calculated from 5–7 day CGM profiles (mean 1275 glucose values per profile) and paired with a corresponding (±1 week) HbA1c measure. In total, 688 average glucose–HbA1c pairs were obtained across pregnancy (mean six pairs per participant). Average glucose level was used as the dependent variable in a regression model. Covariates were gestational week, study centre and HbA1c. Results There was a strong association between HbA1c and average glucose values in pregnancy (coefficient 0.67 [95% CI 0.57, 0.78]), i.e. a 1% (11 mmol/mol) difference in HbA1c corresponded to a 0.67 mmol/l difference in average glucose. The random effects model that included gestational week as a curvilinear (quadratic) covariate fitted best, allowing calculation of a pregnancy-specific eAG (PeAG). This showed that an HbA1c of 8.0% (64 mmol/mol) gave a PeAG of 7.4–7.7 mmol/l (depending on gestational week), compared with a standard eAG of 10.2 mmol/l. The PeAG associated with maintaining an HbA1c level of 6.0% (42 mmol/mol) during pregnancy was between 6.4 and 6.7 mmol/l, depending on gestational week. Conclusions/interpretation The HbA1c–average glucose relationship is altered by pregnancy. Routinely generated standard eAG values do not account for this difference between pregnant and non-pregnant individuals and, thus, should not be used during pregnancy. Instead, the PeAG values deduced in the current study are recommended for antenatal clinical care

Chromatic periodic activity down to 120 MHz in a Fast Radio Burst

Fast radio bursts (FRBs) are extragalactic astrophysical transients whose brightness requires emitters that are highly energetic, yet compact enough to produce the short, millisecond-duration bursts. FRBs have thus far been detected between 300 MHz and 8 GHz, but lower-frequency emission has remained elusive. A subset of FRBs is known to repeat, and one of those sources, FRB 20180916B, does so with a 16.3 day activity period. Using simultaneous Apertif and LOFAR data, we show that FRB 20180916B emits down to 120 MHz, and that its activity window is both narrower and earlier at higher frequencies. Binary wind interaction models predict a narrower periodic activity window at lower frequencies, which is the opposite of our observations. Our detections establish that low-frequency FRB emission can escape the local medium. For bursts of the same fluence, FRB 20180916B is more active below 200 MHz than at 1.4 GHz. Combining our results with previous upper-limits on the all-sky FRB rate at 150 MHz, we find that there are 3-450 FRBs/sky/day above 50 Jy ms at 90% confidence. We are able to rule out the scenario in which companion winds cause FRB periodicity. We also demonstrate that some FRBs live in clean environments that do not absorb or scatter low-frequency radiation.Comment: 50 pages, 14 figures, 3 tables, submitte