Публикации

The Earth’s hydrogen exosphere Lyman-α radiation was mapped with the SWAN/SOHO instrument in January 1996, 1997 and 1998 (low solar activity). The use of a hydrogen absorption cell allowed to disentangle the interplanetary emission from the geocoronal one and to assign the absorbed signal almost entirely to the geocorona. The geocorona was found to extend at least up to 100 Earth Radii (R E ) with an intensity of 5 Rayleigh, an unprecedented distance well exceeding the recent results of LAICA imager (∼50 R E ), and encompassing the orbit of the Moon (∼60 R E ). We developed a numerical kinetic model of the hydrogen atoms distribution in the exosphere which includes the solar Lyman-α radiation pressure and the ionization. The radiation pressure compresses the H exosphere on the day side, producing a bulge of H density between 3 and 20 R E which fits observed intensities very well. The SWAN Lyman-α distribution of intensity was compared both to LAICA (2015) and to OGO-5 (1968) measurements. Integrated H densities of SWAN at a tangent distance of 7 R E are larger than LAICA/OGO-5 by factors 1.1-2.5, while we should expect a stronger effect of the radiation pressure at solar max. We discuss the possible role of H atoms in satellite orbits to explain this apparent contradiction. An onion-peeling technique is used to retrieve hydrogen number density in the exosphere for the three SWAN observations. They show an excess of density versus models at large distances, which is likely due to non-thermal atoms (not in the model).

Приводятся характеристики аппаратно-программного комплекса для лабораторных настроек и ка- либровок плазменных энергомасс-анализаторов, создаваемых в рамках российских и международ- ных космических миссий. Описывается принцип функционирования прибора АРИЕС-Л и приво- дятся результаты функциональных испытаний образцов приборов, полученные с использованием аппаратно-программного комплекса.

Представлены результаты работ по созданию лабораторного прототипа пылеударного масс-анали- затора ПИПЛС-А для проекта “Интергелиозонд”. Прибор предназначен для исследования частиц межпланетной и межзвездной пыли, а также для определения их основных характеристик: массы, компоненты скорости, элементного и изотопного состава. Проведено компьютерное моделирова- ние пылеударного масс-спектрометра, созданы конструкторская модель прибора и рабочее место для испытаний образцов ПИПЛС-А, изготовлен и испытан лабораторный прототип прибора, пред- ставлен анализ полученных результатов.

We report on the monitoring of the final stage of the outburst from the first Galactic ultraluminous X-ray pulsar Swift J0243.6+6124, which reached ˜40 Eddington luminosities. The main aim of the monitoring program with the Swift/XRT telescope was to measure the magnetic field of the neutron star using the luminosity of transition to the `propeller' state. The visibility constraints, unfortunately, did not permit us to observe the source down to the fluxes low enough to detect such a transition. The tight upper limit on the propeller luminosity Lprop < 6.8 × 1035 erg s-1 implies the dipole component of the magnetic field B < 1013 G. On the other hand, the observed evolution of the pulse profile and of the pulsed fraction with flux points to a change of the emission region geometry at the critical luminosity Lcrit ˜ 3 × 1038 erg s-1 both in the rising and declining parts of the outburst. We associate the observed change with the onset of the accretion column, which allows us to get an independent estimate of the magnetic field strength close to the neutron stars surface of B > 1013 G. Given the existing uncertainty in the effective magnetosphere size, we conclude that both estimates are marginally compatible with each other.

The luminosity of accreting magnetized neutron stars can largely exceed the Eddington value due to appearance of accretion columns. The height of the columns can be comparable to the neutron star radius. The columns produce the X-rays detected by the observer directly and illuminate the stellar surface, which reprocesses the X-rays and causes additional component of the observed flux. The geometry of the column and the illuminated part of the surface determine the radiation beaming. Curved space-time affects the angular flux distribution. We construct a simple model of the beam patterns formed by direct and reflected flux from the column. We take into account the possibility of appearance of accretion columns, whose height is comparable to the neutron star radius. We argue that depending on the compactness of the star, the flux from the column can be either strongly amplified due to gravitational lensing, or significantly reduced due to column eclipse by the star. The eclipses of high accretion columns result in specific features in pulse profiles. Their detection can put constraints on the neutron star radius. We speculate that column eclipses are observed in X-ray pulsar V 0332+53, leading us to the conclusion of large neutron star radius in this system (˜15 km if M ˜ 1.4 M⊙). We point out that the beam pattern can be strongly affected by scattering in the accretion channel at high luminosity, which has to be taken into account in the models reproducing the pulse profiles.