Spectroscopic observations of the δ Scorpii binary during its recent periastron passage

The bright star δ Sco has been considered a typical B0-type object for many years. Spectra of the star published prior to 1990 showed no evidence of emission, but only of short-term line profile variations attributed to nonradial pulsations. Speckle interferometric observations show that δ Sco is a binary system with a highlyeccentric orbit and a period of ~10.6 years. Weak emission in the Hα line was detected in its spectrum for the rst time during a periastron passage in 1990. Shortly before the next periastron passage in the summer of 2000, the binary entered a strong Hα emission and enhanced mass-loss phase. We monitored the spectroscopic development of the Be outburst from July 2000 through March 2001. In this paper we present results from our spectroscopy, refine elements of the binary orbit, and discuss possible mechanisms for the mass loss.Fabregat Llueca, Juan, [email protected] ; Blay Serrano, Pedro Jose, [email protected]

The remarkable outburst of the highly-evolved post period-minimum dwarf nova SSS J122221.7−311525

We report extensive 3-yr multiwavelength observations of the WZ Sge-type dwarf nova SSS J122221.7−311525 during its unusual double superoutburst, the following decline and in quiescence. The second segment of the superoutburst had a long duration of 33 d and a very gentle decline with a rate of 0.02 mag d−1, and it displayed an extended post-outburst decline lasting at least 500 d. Simultaneously with the start of the rapid fading from the superoutburst plateau, the system showed the appearance of a strong near-infrared excess resulting in very red colours, which reached extreme values (B − I ≃ 1.4) about 20 d later. The colours then became bluer again, but it took at least 250 d to acquire a stable level. Superhumps were clearly visible in the light curve from our very first time-resolved observations until at least 420 d after the rapid fading from the superoutburst. The spectroscopic and photometric data revealed an orbital period of 109.80 min and a fractional superhump period excess ≲0.8 per cent, indicating a very low mass ratio q ≲ 0.045. With such a small mass ratio the donor mass should be below the hydrogen-burning minimum mass limit. The observed infrared flux in quiescence is indeed much lower than is expected from a cataclysmic variable with a near-main-sequence donor star. This strongly suggests a brown-dwarf-like nature for the donor and that SSS J122221.7−311525 has already evolved away from the period minimum towards longer periods, with the donor now extremely dim

Polaris: History of Pulsation Activity since Discovery

The pulsation activity of small-amplitude Cepheid Alpha UMi (Polaris) during the period of its radial velocity observations has been analyzed. In the 20th century, Polaris was known to demonstrate a decrease in radial velocity amplitude to the minimum, in the 1980s. Thereafter, the amplitude has increased. The observations of September-December 2015 (21 spectra) obtained by 81cm telescope TCO with spectrograph have showed that radial velocity amplitude comes to 4.16 km/s and is approximately twice higher than the estimates made in 2007, with pulsation period adding 8.6 min

THE USE OF CHAOTIC MSK-MODULATION SECURE DATA TRANSMISSION IN A RADIO COMMUNICATION SYSTEM

В работе представлен метод повышения скрытности передачи цифровой информации в системах радиосвязи, который основан на применении хаотических сигналов (процессов) для MSK-модуляции гармонической несущей. Приведена структурная схема устройства формирования и обработки хаотического MSK- сигнала. Проведен анализ качества восстановления информационного сообщения путем расчета вероятности (коэффициента) битовых ошибок, который соизмерим с такими же коэффициентами, полученными для бинарных систем передачи информации, использующих в качестве несущей гармонические колебания. Произведена оценка выигрыша в повышении скрытности информационного сигнала (при помощи BDSстатистики). Показано, что такой способ передачи информации повышает скрытность функционирования системы радиосвязи за счет схожести статистических и динамических характеристик информационного сигнала с аналогичными характеристиками шума наблюдения (белого шума).У роботі отримав розвиток метод підвищення скритності передачі цифрової інформації в системах радіозв'язку, який заснований на застосуванні хаотичних сигналів (процесів) для MSK-модуляції гармонічної несучої. Наведено структурну схему пристрою формування і обробки хаотичного MSK-сигналу. Проведено аналіз якості відновлення інформаційного повідомлення шляхом розрахунку ймовірності (коефіцієнта) бітових помилок який співмірний з такими ж коефіцієнтами, отриманими для бінарних систем передачі інформації що використовують в якості несучої гармонічні коливання. Проведена оцінка виграшу в підвищенні скритності інформаційного сигналу (за допомогою BDS-статистики). Показано, що такий спосіб передачі інформації підвищує скритність функціонування системи радіозв'язку за рахунок схожості статистичних та динамічних характеристик інформаційного сигналу з аналогічними характеристиками шуму спостереження (білого шуму).The paper was developed a method for increasing stealth transmission of digital information in a wireless communication system that is based on the use of chaotic signals (processes) for MSK-harmonic modulation of the carrier. The block diagram of a receiver and a transmitter is shown. The analysis of the quality of the information message recovery by calculating the probability (rate) of bit errors are commensurate with the same coefficients obtained for binary data transmission systems using as a carrier harmonics. The estimation of the gain in increasing secrecy of the information signal (using the BDS-statistic). It is shown that this method of communication increases the stealth operation of radio systems due to the similarity of statistical and dynamic characteristics of an information signal with similar observation noise (white noise)

AMBER/VLTI and MIDI/VLTI spectro-interferometric observations of the B[e]

Astron. & Astrophys., 464, pp. 81-86 (2007)International audienc

VLTI/AMBER and VLTI/MIDI spectro-interferometric observations of the B[e] supergiant CPD-57 2874. Size and geometry of the circumstellar envelope in the near- and mid-IR

Astron. & Astrophys., 464, pp. 81-86 (2006)International audienc