Astronomische Nachrichten最新文献

This study discusses historical records of Korea that mention “stars” possibly related to astronomical transient events. We selected 19 such records and scrutinized them by cross-checking with records of other countries to identify those events. Ten events were identified as comets based on their described motions and tails. We further confirmed this by comparing them with records from other countries. Five events were classified as meteors based on descriptions of their movements, sizes, and shapes. We speculate that two recordings about “big stars” (大星) are typographical errors for “Mars” (火星), as the descriptions of these big stars seem to be consistent with the properties of the latter. This leaves two unidentified events, and we search lists of astronomical transients for their counterparts. Our work emphasizes the uncertainties and challenges caused by the limited information in the historical records while exploring the usefulness of historical records to enhance the understanding of astrophysical transient events.

Astrophysical accretion discs that carry a significant mass compared with their central object are subject to the effect of self-gravity. In the context of circumstellar discs, this can, for instance, cause fragmentation of the disc gas, and—under suitable conditions—lead to the direct formation of gas-giant planets. If one wants to study these phenomena, the disc's gravitational potential needs to be obtained by solving the Poisson equation. This requires to specify suitable boundary conditions. In the case of a spherical-polar computational mesh, a standard multipole expansion for obtaining boundary values is not practicable. We hence compare two alternative methods for overcoming this limitation. The first method is based on a known Green's function expansion (termed “CCGF”) of the potential, while the second (termed “James' method”) uses a surface screening mass approach with a suitable discrete Green's function. We demonstrate second-order convergence for both methods and test the weak scaling behavior when using thousands of computational cores. Overall, James' method is found superior owing to its favorable algorithmic complexity of $��\sim �O�\left(n^3\right)�$ compared with the $��\sim �O�\left(n^4\right)�$ scaling of the CCGF method.

The Nebra Disk is one of the earliest astronomical manifestations of humanity in Central Europe. We interpret the striking sevenfold stellar group shown on the disk as a celestial conjunction of the five naked-eye visible planets together with Pollux and Castor in the constellation Gemini (happening in 2210BC) and the dominating large, filled circle as a bright supernova, probably corresponding to the remnant 3C58 in Cassiopeia. We believe that a close coincidence of these two extremely rare celestial events, that does never happen more than once in a human lifetime, could have impressed people of that epoch in a way that it was conveyed orally over several generations, until some Bronze Age artist created the Nebra Disk. If this interpretation is correct, it could offer a rather exact dating of a supernova explosion observed about 4200 years ago, more precise than any other dating methods for past supernova events, possibly leading to significant new insights into the underlying physics of supernovae.

We introduce a new solar feed for the PEPSI nighttime spectrograph of the LBT. It enables spectroscopy of the Sun-as-a-star in circular polarization (CP) and linear polarization (LP) with a spectral resolution of 250,000 (≈0.025Å or $��600��m��s^{�-�1�}�$) for the wavelength range 383–907 nm. The polarimeter is a dual-beam design with a modified Wollaston prism as beam splitter and linear polarizer combined with a retractable super-achromatic $��\lambda �/�4�$ retarder. The Wollaston beam diameter is 14 mm and large enough that it does not require a classical telescopic feed anymore. Both polarimetric beams are re-imaged into respective integration spheres from which two fibers feed the scrambled light to the spectrograph. The system is fully automated in the sense that it finds the Sun in the morning, closes the guider loop, observes a predefined number of individual spectra, and moves to a home position at the end of the day. Among the scientific aims is Zeeman–Doppler imaging of the Sun as a star over the next activity cycle. Our first-light application detects a clear Stokes-V/I profile with a full amplitude of $��1�\times �{10}^{�-�4�}�$ on, for example, October 13, 2023, suggesting a solar disk-averaged line-of-sight net magnetic field of +0.37±0.02 G. Comparison of this value with a contemporary full-disk line-of-sight magnetogram suggests an unsigned mean field of about ≈13 G.

In this study, spectral, age, kinematic, and orbital dynamical analyses were conducted on metal-poor and high proper-motion (HPM) stars, HD 8724 and HD 195633, selected from the Solar neighborhood. This analysis combines detailed abundance measurements, kinematics, and orbital dynamics to determine their origin. Standard 1D local thermodynamic equilibrium analysis provides a fresh determination of the atmospheric parameters: T_{eff =} 4700 ± 115 K, log g = 1.65 ± 0.32 cgs, [Fe/H] = −1.59 ± 0.04 dex, and a microturbulent velocity $��\xi �=�$ 1.58 ± 0.50 km s⁻¹ for HD 8724 and T_eff = 6100 ± 205 K, log g = 3.95 ± 0.35 cgs, [Fe/H] = −0.52 ± 0.05 dex, and $��\xi �=�$1.26 ± 0.50 km s⁻¹ for HD 195633. The ages were estimated using a Bayesian approach (12.25 Gyr for HD 8724 and 8.15 Gyr for HD 195633). The escape scenarios of these stars from 170 candidate globular clusters (GCs) in the Galaxy were also investigated because of their chemical and physical differences (HPM and metal-poor nature). Accordingly, the calculated probability of encounter (59%) for HD 8724 at a distance of five tidal radius suggests that star HD 8724 may have escaped from NGC 5139 ($��\omega �$ Cen), supported by its highly flattened orbit and may belong to a subpopulation of this GC. Conversely, HD 195633's kinematics, age, and metal abundances point toward an escape from the bulge GC NGC 6356.

The pulsating variable star Mira (o Ceti) was observed by David Fabricius (Frisia) in 1596 and 1609. We review suggested previous detections (e.g., China, Hipparchos). We analyze all Mira records from Fabricius in their historical context. Fabricius measured the separation of Mira to other stars to ±1.6−1.7′. From his texts, we derive a brightness (slightly brighter than Hamal) of ca. 1.9±0.1 mag and a color index B-V$��\simeq �$1.3−1.4 mag (‘like Mars’) for 1596 Aug 3 (Jul.). Mira started to fainten 19 days later and was observed until mid/late Oct. We show why such a red star cannot be followed by the naked eye until ca. 6 mag: For Mira's color at disappearance and altitude from Frisia, the limit is reduced by ca. 1.0 mag. Since Fabricius connected the Mira brightening with the close-by prograde Jupiter, he re-detected it only 12 years later, probably shortly before a relatively bright maximum—discoveries are strongly affected by biases. A Mira period of 330.2 days is consistent with both the oldest data (from Fabricius 1596 to Hevelius 1660) and the most current data (VSX 2004–2023), so that we see no evidence for secular period or phase shifts. (We also present Fabricius' observations of P Cygni in 1602.)