Astronomy Reports最新文献

As part of the Early Science Program of the RadioAstron project, the millisecond pulsar B1937+21 was observed in October 2012. The total duration of the experiment supported by eight ground-based radio telescopes was about three hours. The radiation in both circular polarizations in the frequency band of 1644‒1676 MHz was recorded. Characteristic time and frequency scales of scintillation caused by the scattering on the interstellar plasma density fluctuations have been measured: (Delta {{t}_{{{text{dif}}}}} = 275.2 pm 0.1) s and (Delta {{nu }_{{{text{dif}}}}} = 580 pm 30) kHz. The angular diameter of the scattering disk, ({{theta }_{{text{H}}}} = 0.32 pm 0.03) mas, has been estimated from the decrease in the amplitude of the interferometric response at the ground–space baselines. The dependence of the visibility amplitude on the delay shows two scattering time scales: ({{tau }_{{{text{sc}}1}}} = 110 pm 30) ns and ({{tau }_{{{text{sc}}2}}} = 750 pm 100) ns, which indicates an ellipse-like scattering disc with an axis ratio of 2.6 : 1. The drift of the visibility maximum on the residual interference frequency that was observed at the intercontinental baselines can be explained by atmospheric effects, while the dominant contribution being the additional phase shift in the troposphere above European stations.

The problem of registration of collapsing stars in the Galaxy is considered using two instruments: the optoacoustic gravitational detector OGRAN and the neutrino telescope BUST, located in the underground laboratories of the Baksan Neutrino Obstrvatory of the Institute for Nuclear Research of the Russian Academy of Sciences (BNO INR RAS). An algorithm for joint data processing on the experience of registration of the SN1987A event is presented. The proposed method is illustrated by the current output signals of these instruments.

We present multiwavelength analysis of the pre-flare phase, as well as the onset of the powerful X4.9 near-limb eruptive solar flare on February 25, 2014 (SOL2014-02-25T00:39), revealing the tether-cutting geometry. This event provides an excellent opportunity to investigate pre-flare and flare energy release in details utilizing available large volume of observational data in different spectral ranges, suitable limb position of the flare, high power of its energy release, favorable spatial distribution of pre-flare and flare emission sources and well-observed eruption. We aim at determining relationship between the region of pre-flare energy release with the regions where the flare started to develop, and to investigate a detailed chronology of energy release during the pre-flare time interval and the beginning of the impulse phase. Using X-ray, ultraviolet (UV) and radio microwave data we found that the pre-flare energy release site was compact and localized in the vicinity of interaction (tether-cutting type) of larger-scale magnetic structures near the polarity inversion line of the magnetic field. The analysis indicates that a pre-flare current sheet could be in this region. Good correspondence between the location of the pre-flare and flare emission sources visible at the very beginning of the impulsive phase is shown. We found relationship between dynamics of the energy release in the pre-flare current sheet and formation of the future flare eruptive structure. The growth of the magnetic flux rope was associated with activation of plasma emissions, flows and an increase of UV radiation fluxes from the region where the pre-flare current sheet was located. The eruptive flux rope gradually grew due to “feeding” by magnetized plasma ejected from the reconnecting pre-flare current sheet. Finally, it is shown that the most probable trigger of the eruption was a local fast microflare-like magnetic reconnection in the pre-flare current sheet. Some local instability in the pre-flare sheet could lead to a transition from the slow to fast reconnection regime. As a result, an ejection from the sheet was initiated and the eruptive flux rope lost its stability. Then, the eruptive flux rope itself initiated formation of the main reconnecting flare current sheet as in the Standard Flare Model (under the flux rope) during its movement, and intense emissions associated with the impulsive phase were observed.

In the paper, archival data of the RadioAstron ground–space interferometer project concerning observations of radiation in the OH hydroxyl lines (1665 and 1667 MHz transitions) in the Cep A source have been analyzed. The observations have been carried out on January 7, 2013. The duration of the observation session was about one hour. Ground-based radio telescopes at the Zelenchuk Observatory (Special Astrophysical Observatory of the Russian Academy of Sciences, North Caucasus, Russian Federation), in Yevpatoria (Crimea, Russian Federation), and at the Torun Astronomy Center (Republic of Poland) have participated in the observations. No interferometric response has been detected at the ground–space bases. Several compact sources with angular sizes from 10 to 20 milliarcseconds have been detected at the base between the radio telescopes in Torun and at the Zelenchuk Observatory. These angular sizes correspond to linear sizes of 7.5–15 astronomical units (AU). It has been shown that the detected compact sources are distributed over a region of 750–1500 AU.

The aim of this study is to investigate the interaction of Earth-mass planets with a disk of planetesimals. It is shown that an Earth-like planet, initially located near the inner boundary of the planetesimal disk, migrates inside the disk. The magnitude of penetration of the planet into the disk is a random value determined by the angular momentum distribution of planetesimals approaching the planet. However, at a certain stage, the direction of the planet’s migration always changes, and the planet returns to the inner boundary of the disk. During such reversible migration, the planet perturbs the orbits of planetesimals and increases their relative velocities in the region of the disk where it was during its migration. The relative velocities of planetesimals increase to values sufficient for their fragmentation during collisions. Our estimates show that after the passage of an Earth-mass planet through the outer planetesimal disk (30–40 AU in our model), the average relative velocities in the main part of the disk increase to values sufficient for the fragmentation of monolithic basaltic planetesimals ~40 km in size. Thus, the interaction of even a small planet (of the order of Earth’s mass) with a planetesimal disk can lead to the formation of dust particles observed in outer debris disks.

A review of publications devoted to the study of the characteristics of the Radcliffe wave has been given. The advent of mass measurements of radial velocities of stars has recently led to a number of interesting results obtained from the analysis of spatial velocities of stars and open star clusters. An important place in the study has been given to issues related to the clarification of the direct or indirect influence of magnetic fields on the process of formation of the Radcliffe wave. The hypothesis of Parker instability of the galactic magnetic field as one of the reasons for the formation of wave-type inhomogeneities in the galactic disk has been discussed.

An analysis of observations of the pulsar B1237+25 at a frequency of 111 MHz has been presented. The observations have been carried out with the Large In-Phase Antenna (LPA) of the Pushchino Radio Astronomical Observatory, Lebedev Physical Institute. A new component in the average profile in the central region of the emission has been detected. This component with a half-width of 1.6 ms has been observed against the background of a more extended component with a half-width of 7 ms. This new component of the average profile at a frequency of 111 MHz manifests itself in all modes of the pulsar radio emission: quiet-normal (QN), flare-normal (FN), and in the abnormal mode (AB), while in the abnormal mode, it has also been detected by other observers at other frequencies. The drift of subpulses is observed in the normal mode of emission only in the extreme components of the average profile. The normal mode is interrupted by nullings and transitions to the abnormal mode AB. In the AB mode, the structure of the activity zones at the edge of the outer cone is destroyed, the distance between the inner and outer cones increases almost twice, and the distance between the inner cone and the central region decreases. An analysis of our data has shown that the components of the outer and inner cones of the average profile are formed by the ordinary mode of radio emission (O-mode) and constitute a single cone emission of the pulsar. The central components of the average profile (wide and narrow) are formed by the extraordinary mode of emission (X-mode). Estimates of the height of the emission from the central region (X-mode) and the cone emission (O-mode) are obtained: 80 and 370 km, respectively. A microstructure with a submicrosecond time scale of ({{tau }_{mu }} leqslant 0.5 mu s) was discovered. Such a time scale corresponds well to the characteristic time of spark discharge development in the polar cap. For this value of ({{tau }_{mu }}), the vacuum gap height must be ({{h}_{p}} leqslant 750) cm. Based on the steepness of the trailing edge of an individual pulse at the longitude of the first component, a limit on the value of the (gamma ) factor of the relativistic secondary plasma was obtained: (gamma geqslant 260). The analysis showed that in 88% of cases, the normal mode (N) is realized, and in 81% of them—the QN mode and only in 19% the FN mode. The AB mode is only 12%. The dependence of the distance between the components of the outer and inner cones of radiation on the frequency is the same and corresponds to a power law with an index of –0.16.

The results of absorption modeling in the hydrogen Hα 6563 Å and helium 10830 Å lines for hot Jupiter HAT‑P-32b have been presented. The modeling has been performed using a three-dimensional hydrodynamic code together with the Monte Carlo model of Lyα photon transport. A wide range of stellar radiation and atmospheric parameters has been considered. It has been found that the measured spectrally resolved transit absorption in both lines can be well described by model calculations with the stellar radiation in the XUV range limited to 200 erg/cm²/s per 1 AU, the helium content in the planet’s atmosphere is He/H = 2/98, and metallicity is [Fe/H] = –1. It has been shown that absorption in the helium line occurs uniformly in a large volume of the outflowing atmosphere, and in the hydrogen line, it occurs in a layer of 1.5–2.75 planet radii.

In the study, the dynamical stability of 41 eclipsing binary (EB) systems proposed to host one or two additional bodies was examined, as reported in the literature. Using the REBOUND N-body integration package, we employed the WHFast and IAS15 integrators alongside the MEGNO (Mean Exponential Growth Factor of Nearby Orbits) indicator to conduct detailed orbital stability simulations over a period of 10 Myr. For systems exhibiting signs of instability on shorter timescales, MEGNO analyses were performed to identify chaotic behavior more effectively. Of the 41 systems analyzed, all 31 systems with a single proposed additional body demonstrated stable (non-chaotic) orbital configurations. Conversely, among the 10 systems proposed to host two additional bodies, only FK Aql exhibited stability, while the remaining systems displayed chaotic behavior, highlighting the challenges of maintaining long-term stability in multi-companion configurations. MEGNO analyses for FK Aql over 10⁸ years confirmed its placement in a dynamically stable region, with MEGNO chaos parameter values ((langle Yrangle leqslant 2)), consistent with its orbital stability timeline. In contrast, MEGNO maps for the remaining multi-companion systems corroborated their chaotic timelines, confirming their instability. The combination of orbital stability timelines and MEGNO maps provides complementary insights into the long-term dynamics of these systems. This approach underscores the necessity of incorporating stability analyses into studies of binary systems to refine our understanding of their complex gravitational interactions.

A model for co-rotating interaction regions of multispeed solar wind flows including a region with a reduced level of small-scale turbulence in front of the compressed part has been proposed. This model is a development of the previously proposed model for the leading part of the interaction region. Dynamic two-dimensional maps of the distribution of the interplanetary scintillation level adapted to observations using the LPA LPI radio telescope have been calculated based on the model. As an example, an event related to a magnetic storm on April 16–17, 2024 has been considered. A comparison of model calculations with observational data, which confirmed the previously made assumption that the scintillation attenuation at night before the arrival of a disturbance to the Earth is associated with an area of reduced small-scale turbulence, has been carried out. In general, the qualitative model calculations are in good agreement with the observational data.