Astronomische Nachrichten最新文献

The Vela pulsar is a young neutron star with spin period of P = 89 ms and a measured low braking index (˜1.4) that is much less than the standard value of 3 predicted by the magnetic dipole radiation (MDR) model; however, its spin period evolution has been a mystery. In this article, we assume that the spin-down of the Vela pulsar is attributed to both MDR and wind flow (hereafter MDRW), and find that the ratio of wind flow to the magnetic dipole radiation is about 80%, which is higher than that of the Crab pulsar (25%). In other words, the spin-down torque of the Vela pulsar is dominated by the wind flow. The spin period (P) evolution of the Vela pulsar depends on its real age, where its supernova remnant age is assumed to be an indicator of its true age, estimated from 10 to 20 kyr, and then we obtain their initial spin periods of ˜53.89 and ˜20.90 ms, respectively, which are consistent with the observed initial spin period ranges of young pulsars. Furthermore, we find that the Vela-like pulsar by MDRW can evolve to the long spin period of a thousand of seconds in less than million years, which can conveniently help the astronomers understand the recently observed ultra-long period radio pulsars like GPM J1839-10 (P = 21 min), GLEAM-X J1627 (P = 18 min), as well as PSR J0901+4046 (P = 76 s).

We present the orbit and the mass estimates for the components of the visual binary star 61 Cyg obtained with the positional observations, including the high-precision Gaia data, and the measurements of differences in the radial velocities and the radial accelerations of the components. Since the orbital period of this star significantly exceeds the period of observations, using the radial velocities and the radial accelerations allows us to reduce uncertainty in the determination of the orbital elements and the total mass of the system.

The Generalized Uncertainty Principle (GUP) is motivated by the premise that spacetime fluctuations near the Planck scale impose a lower bound on the achievable resolution of distances, leading to a minimum length. Inspired by a semiclassical method that integrates the GUP into the partition function by deforming its phase space, we induce a modification on the thermodynamic quantities of the MIT bag model that we propose serves as an effective semiclassical description of deconfined quark matter in a space with minimal length. We investigate the consequences of this deformation on the zero-temperature limit, revealing a saturation limit for the energy density, pressure, and baryon number density and an overall decrease of the thermodynamic quantities which suggests an enhanced stability against gravitational collapse. These findings extend existing research on GUP-deformed Fermi gases. Ultimately, our description introduces the effects of quantum gravity in the equations of state for compact stars in a mathematically simple manner, suggesting the potential for extension to more complex systems.

Prime-focus catadioptric astrographs have been used for a long time in various astronomical applications. The prime advantage offered by them is the capability to produce remarkably wide fields of view, and hence generate a huge amount of data in relatively less observation time. An emerging application of such wide-field astrographs is in the form of telescope arrays. While this has been implemented mostly, using commercial refractive lenses, low-cost catadioptric objectives can be used as an alternative for wide-field or high-contrast array applications. Commercial catadioptric systems are generally available as modifications of Schmidt and Maksutov systems, that too, mostly in the Cassegrain configuration. Here, we present a low-cost alternative prime focus camera design of Richter–Slevogt configuration, which is in turn an extension of the Houghton correctors. The Richter–Slevogt design has the potential for a very high performance due to several degrees of freedom. The presented one is a 150 mm aperture, $��f�/�3�$ system, providing 3.5° (circular) diffraction-limited FOV (strehl $��\ge �0.85�$), using only standard glasses, N-BK7 and F2. We present the performance analysis, tolerance sensitivity, and statistical (Monte-Carlo) analysis for this design. Potential applications of the system, other than as an array are also briefly discussed.

The visual binary system 16 Cyg A+B consists of similar solar twins, but a planetary companion is detected only in B. An intensive spectroscopic differential analysis is carried out to the Sun, 16 Cyg A, and 16 Cyg B, with particular attention being paid to (i) precisely establishing the differential atmospheric parameters/metallicity between A and B, and (ii) determining the important CNO abundances based on the lines of CH, NH, and OH molecules. The following results are obtained. (1) The Fe abundances (relative to the Sun) are [Fe/H]^A = +0.09 and [Fe/H]^B = +0.06 (i.e., A is slightly metal-rich than B by +0.03 dex). This lends support to the consequences of recently published papers, while the conclusion once derived by the author (almost the same metallicity for A and B) is acknowledged to be incorrect. (2) The differential abundances ($��\Delta �$[X/H]) of volatile CNO with low $��T_c�$ (condensation temperature) are apparently lower than those of refractory Fe group elements of higher $��T_c�$, leading to a positive gradient in the $��\Delta �$[X/H] versus $��T_c�$ relation being more conspicuous for A than B. This is qualitatively consistent with previous studies, though the derived slope is quantitatively somewhat steeper than that reported by other authors.

Cosmic rays are a very valuable tool of multi-messenger astrophysics, as they provide a very different picture of the sky. During the past decades, a large number of active astrophysical objects in our Galaxy and beyond have been discovered through the detection of gamma-rays with Cherenkov telescopes. Cosmic rays, neutrinos have been successfully supplementing the astronomical view. Also, cosmic rays may offer to investigation of the elementary particle properties. Neutrino telescope detects the Cherenkov radiation generated in water or ice by the passage of relativistic charged particles produced by neutrino collisions with nucleons in the detector volume. Some alternative approaches have been proposed. One of them is using earth matter or mountains as a target volume for the conversion of neutrinos to leptons which then initiate extensive air showers (EAS) in the atmosphere, then showers can be detected by the Cherenkov telescope. Investigations with SHALON Cherenkov telescope have included observations of EAS from the sub-horizontal direction $��\Theta �=�97�°�$. Five EAS of ∼10 TeV energies were detected with SHALON from the sub-horizontal directions in the conditions with the zero expected number of showers. These events may be caused by the decay of a long-lived penetrating particle entering the atmosphere from the ground and decaying in front of the telescope. As a possible explanation, two scenarios with an unstable neutrino of mass $��m�\approx �0.5�$ GeV and $���c�\tau ��\approx �30�$ m is discussed. Remarkably, one of these models has been proposed to explain an excess of electron-like neutrino events at MiniBooNE.

The investigation of supernova remnants (SNRs) across the electromagnetic spectrum from radio up to very high energy gamma-rays can serve as a test of the particle acceleration and touches on one of the unresolved problems of modern astrophysics, namely the origin of cosmic rays and the Galaxy's contribution to the overall cosmic ray spectrum. The multiwavelength observations of Cas A SNR demonstrated that structure and spectral features have clear signs of young SNRs and its overall properties make this object the best target to test a hypothesis of cosmic ray origin in SNRs. Studies of Cas A at very high energies by SHALON telescope showed the location of TeV gamma-ray emission region relative to the position of reveres shock. Also, the spectral energy distribution was obtained at high and very high energies. To describe the spectral and structural features of this SNR viewed in non-thermal emission, two approaches involving reverse and also both reverse and forward shocks to the mechanism of diffusive shock acceleration of cosmic rays in Cas A were applied. It is demonstrated that the observational properties of Cas A are well reproduced by the hadronic model with significant contribution of both the forward and reverse shocks in the generation of broadband emission. Calculation results suggest that the very high efficiency of particle acceleration in Cas A, which value is up to 25% of the supernova explosion energy with energy of accelerated particles not exceeding of $��{10}^{14}�-�{10}^{15}�$ eV. Whereas, the forward shock model predicts the spectral characteristics of the TeV-gamma-emission corresponding to ones detected at 800 GeV–40 TeV that are the evidence of acceleration of the hadronic cosmic rays in shells of SNRs up to $��{10}^{17}�$ eV

The investigation of very high energy gamma-ray sources touches on the problem of the cosmic ray origin and the role of the Galaxy in their generation. The SHALON observations have yielded the results on $��\gamma �$Cygni SNR Galactic supernova remnant. The observation results are presented with spectral energy distribution and emission map by SHALON in comparison with other experiment data obtained by ROSAT in x-ray energy range, radio-data by CGPS, and also observations of GeV–TeV gamma-rays by Fermi LAT. The overall $��\gamma �$Cygni SNR characteristics detected in radio, x-rays, and GeV–TeV gamma-rays can be a result of the shocks at the interaction of the supernova ejecta and the surrounding medium. The collected experimental data help to make clear the origin of TeV $��\gamma �$-ray emission in the $��\gamma �$Cygni SNR. The density of target material in the SNR surroundings is enough to produce the observable TeV gamma-ray flux via the shock acceleration of hadrons in the detected regions. The detection of gamma-ray emission at 0.8–60 TeV from the North-West and South-East shells of $��\gamma �$Cygni SNR by SHALON would favor the hadronic origin of the gamma-rays in this supernova remnant.