Astronomische Nachrichten最新文献

We exploit the astro-photometric dataset of the multi-epoch infrared parallel field of a Hubble Space Telescope Large Programme aimed at studying the faintest stars of the globular cluster NGC 6752 to determine the luminosity and mass functions of the multiple stellar populations of this cluster. Thanks to the measurement of proper motions and deeper completeness, the results presented in this paper represent a significant improvement over those of previous studies. We successfully derived membership probabilities reaching stars as faint as $��m_{�F�160�W�}�\sim �25�$, allowing us to reliably distinguish the three main stellar populations detected within this cluster. We employed a new set of model isochrones that have been individually fit to the colour–magnitude diagram of each population. We present a comprehensive analysis of the luminosity and mass functions for three stellar populations within NGC 6752. Notably, our findings reveal differences in the present-day luminosity and mass functions of first-generation and second-generation stars; these differences are consistent with the manifestation of the effects of dynamical processes acting on populations with different initial spatial distributions. Finally, we publicly release the catalogues with positions, photometry, proper motions and memberships probabilities, as well as the stacked-image atlases and all newly calculated stellar models.

It has been proposed that the building blocks of pulsar matter could be ‘an’, strangeons analogy of atomic nucleons but with negative strangeness. A bare strangeon star should not have a smooth surface, but be covered with small hills (‘zits’), as indicated by red spots in this schematic illustration. These zits on the pulsar surface might be responsible for the magnetospheric activity and the mysterious coherent radio emission, as discussed in the contribution by Xu and Wang, this issue, p. e230153. Zits may also be responsible for the significantly non-symmetrical sparking discovered in the 110-min polarization observation of pulsar PSR B0950+08 targeted with China's Five-hundred-meter Aperture Spherical radio Telescope, FAST. Details can be found in the contribution by Wang et al., this issue, e240010.

We outline our experience in organizing the first edition of the Workshop on Matter, Astrophysics, Gravitation, Ions and Cosmology, held in virtual and in-person format, denominated MAGIC23, held from 6 to 10 March, 2023, in Praia do Rosa, Santa Catarina, Brazil. The event aimed to bring together leading academic scientists, professors, students, and research scholars for exchanging experiences and discuss the most recent innovations, trends, practical challenges, and experimental and theoretical solutions adopted in the investigation fields within the scope of the meeting. The workshop offered to the participants a platform for scientific and academic projects, partnerships, and presentation of high-quality research contributions describing original and unpublished results on topics related to matter, astrophysics, gravitation, ions, and cosmology.

The magnetic field in the O9.7 V star HD 54879 has been monitored for almost a decade. Spectropolarimetric observations reveal a rather strong mean longitudinal magnetic field that varies with a period of about 7.41 years. Observations in the H$��\alpha �$ line show a variation with the same period, while the H$��\beta �$ line shows only little variation. Assuming the periodic variation to be caused by a slow rotation and a dipolar magnetic field, we find a magnetic field strength of $��\ge �$2 kG at the magnetic poles. With the relatively low mass loss rate of $��{10}^{�-�9�}�M_{\odot }�$ year⁻¹, this star is a case of extremely strong magnetic confinement. Both theoretical arguments and numerical simulations indicate the presence of an extended disk of increased gas density in the equatorial plane of the magnetic field, where gas from the line-driven stellar wind is trapped. This disk is likely to be the origin of the observed H$��\alpha �$ emission, which peaks together with the strongest line-of-sight magnetic field. The profile of the H$��\alpha �$ line is resolved in several components and shows a remarkable variability with the rotation period.

Motion on the sky of the brown dwarf binary system Luhman 16 AB. At a distance of less than 2 pc, it is known as the nearest pair of this type to Earth. (Top:) The entire 4.7ʹ × 4ʹ region surrounding Luhman 16 AB, as monitored by HST. (Bottom:) Zoom-in of the 25ʺ × 7ʺ rectangular region indicated in red in the top panel, showing the complete trajectory in the sky of Luhman 16 A and B during the period of 7.4 years monitored by recent HST observations. The astrometric solution for the Luhman AB barycenter, with and without parallax is indicated by blue and magenta curves, respectively. For details about the search for a suspected exoplanet orbiting one of the brown dwarf components see Bedin et al., this issue, e230158.

We performed spectroscopic and photometric analyses on the early B-type LP Ori young stellar object located in the Orion Nebula. The high-resolution spectra of LP Ori was obtained at the Ankara University Kreiken Observatory in 2023, while all spectra recorded over the past 19 years were extracted from the ESO and ESPaDOnS archives. In these spectra of LP Ori, there is typically an emission observed in the core of the Balmer profile. This structure is accompanied by a $��\sim �$14-year interval inverse P-Cygni repetition superimposed on the Balmer profile. Additionally, an emission in the $��\lambda �$5,875 He I line is visible in the spectra in the year 2023. When this emission is considered together with the inverse P-Cygni structures, these observations suggest that LP Ori is a Herbig Ae/Be star. The abundance pattern of LP Ori is close to solar with the exception of a slightly rich helium and slightly poor aluminum abundance. Additionally, the spectral energy distribution of LP Ori was constructed to confirm the infrared excess caused by its circumstellar disk. Furthermore, the photometric analysis performed on the TESS observations of LP Ori shows significant photometric variability and the frequency analysis reveals a $��\beta �$ Cephei star in its forthcoming evolution.

We present chemical abundances of the very bright metal-poor star HD 1936 based on high-resolution and high SNR spectra from AUKR. We obtain the abundances of 29 atomic species with atomic numbers between 3 and 63. In this context, the derived lithium abundance of 1.01 is consistent with the thin Li plateau observed in lower red giant branch stars. The star is a carbon-normal with a ratio of −0.31, just like other low-luminosity red giants on the thin Li plateau. We find the ratios of [Eu/Fe] = 0.43 and [Ba/Eu] = −0.64, indicating very little s-process contamination. These ratios allow us to classify the star as a moderately r-process-enhanced (r-I) metal-poor star for the first time. It is worth mentioning that the star has a metallicity of −1.74, a [Cu/Fe] of −0.74, a [Zn/Fe] of 0.04, and a [Mg/C] of 0.69. The results suggest that it may be a second-generation star formed in a multi-enriched environment, rather than being a descendant of very massive first-generation stars. A last point worth mentioning is the possibility that HD 1936 may host a sub-stellar component with a mass of $��18.35�M_J�$. Although our study does not confirm or deny this, we briefly discuss the possibility of the star hosting a planet.