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The Atacama Large Millimeter/submillimeter Array (ALMA) allows for solar observations in the wavelength range of 0.3–10 mm, giving us a new view of the chromosphere. The measured brightness temperature at various frequencies can be fitted with theoretical models of density and temperature versus height. We use the available ALMA and Metsähovi measurements of selected solar structures (quiet sun (QS), active regions (AR) devoid of sunspots, and coronal holes (CH)). The measured QS brightness temperature in the ALMA wavelength range agrees well with the predictions of the semiempirical Avrett–Tian–Landi–Curdt–Wülser (ATLCW) model, better than previous models such as the Avrett–Loeser (AL) or Fontenla–Avrett–Loeser model (FAL). We scaled the ATLCW model in density and temperature to fit the observations of the other structures. For ARs, the fitted models require 9%–13% higher electron densities and 9%–10% higher electron temperatures, consistent with expectations. The CH fitted models require electron densities 2%–40% lower than the QS level, while the predicted electron temperatures, although somewhat lower, do not deviate significantly from the QS model. Despite the limitations of the one-dimensional ATLCW model, we confirm that this model and its appropriate adaptations are sufficient for describing the basic physical properties of the solar structures.

We report a radio and optical study of the star TYC 6544-3483-1 originally selected as a follow-up target in the course of our efforts to cross-identify Galactic high-energy sources. The star by itself finally turned out to be a very ordinary main-sequence star despite the initial expectations that apparently pointed to the contrary. We found that its, at first glance, exotic properties arise as a combined consequence of the limited angular resolution of the radio and optical databases being used. Our preliminary astrophysical interpretation was strongly hampered by the presence of unexpected optical variables inside both the photometric and background apertures. While such an ill-posed situation is not a frequent one, we believe that our experience is worth sharing with the community to raise a word of caution and help to avoid similar misleading results, especially when dealing with modern TESS data.

We present optical spectroscopic and photometric observations of type II SNe 2019vxm and 2020tlf. The photometric monitoring of SN 2019vxm continued for 592 days, two spectra were collected. SN 2020tlf was observed for 163 days and we obtained one spectra. The maximum luminosity of both SNe is high: $��M_V�=�-�20.0�,�-�18.33�$ mag for SN 2019vxm and SN 2020tlf, respectively. SN 2019vxm displays typical for most of SNe IIn photometric evolution: long rise to the maximum and slow brightness decline with several changes of the decline rate. The light curve of SN 2020tlf shows it may be considered as an intermediate object between classes II-P and II-L. The spectral evolution of SN 2019vxm was typical for SNe IIn, while for SN 2020tlf only weak signs of circumstellar interaction were observed at maximum light.

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.