Astronomische Nachrichten最新文献

We investigate outflows and the physics of super-Eddington versus sub-Eddington regimes in black hole systems. Our focus is on prospective science using next-generation high-resolution soft x-ray instruments. We highlight the properties of black hole ultraluminous x-ray source (ULX) systems in particular. Owing to scale invariance in accreting black holes, ULX accretion properties, including their outflows, inform our understanding not only of the closely related population of (similar-mass) x-ray binary systems but also of tidal disruption events (TDEs) around supermassive black holes. A subsample of TDEs are likely to transcend super-Eddington to sub-Eddington regimes as they evolve, offering an important unifying analog to ULXs and sub-Eddington x-ray binaries. We demonstrate how next-generation soft x-ray observations with resolving power $��\gtrsim �1000�$ and collecting area $��\gtrsim �1000��{\mathrm{cm}}^2�$ can simultaneously identify ultrafast and more typical wind components, distinguish between different wind mechanisms, and constrain changing wind properties over characteristic variability timescales.

Variability of the Hα emission line profile of the magnetic O-type star HD 54897 over one decade, from 2014 to 2024. In the left panels, each profile is plotted with a different color as is indicated in the legend, showing the corresponding observing date and instrument used: H: HARPS, E: ESPaDOnS, U: UVES, and P: PEPSI. The upper panel shows the profiles based on the spectra observed recently, while the bottom panel shows all available profiles published previously. The right panel shows the same data in a color scale plot. The red color corresponds to the strongest emission, while the blue color shows the Hα line wings appearing in absorption. The observed Hα emission is thought to originatein a disk of increased gas density in the equatorial plane of the magnetic field. For details see the article by Küker et al., this issue, e230169.

The dynamical evolution of tight star-planet systems is influenced by tidal interactions between the star and the planet, as was shown recently. The rate at which spins and orbits in such a system evolve depends on the stellar and planetary tidal dissipation efficiency. Here, we present a method to constrain the modified tidal quality factor $��Q_{*}^{\prime }�$ of a planet-hosting star whose rotational evolution has been altered by its planet through angular momentum transfer from the planetary orbital motion to the rotation of the stellar convective zone. The altered rotation is estimated from an observed discrepancy of magnetic activity of the planet-hosting star and a coeval companion star, that is, this method is applicable to star-planet systems with wide stellar companions. We give an example of the planet-hosting wide binary system HD189733 and find that the planet host's modified tidal quality factor is constrained to be $��Q_{*}^{\prime }�\le �2.33�\times �{10}^7�$.

The poorly studied variable star V390 Sco, previously classified as a Mira pulsator, was detected in a brightening event by the ESA Gaia satellite in September 2023. This work presents an analysis of available archival multifrequency photometric data of this target, along with our spectroscopic observations. Our findings lead to the conclusion that V390 Sco is a new symbiotic star identified by Gaia, currently undergoing a classical symbiotic outburst. Additionally, we uncovered three prior outbursts of this system through archival photometry. The outbursts recur approximately every 2330–2400 days, and we hypothesize the periastron passage in an eccentric orbit may trigger them, similarly to the case of BX Mon, DD Mic, or MWC 560. A detailed investigation into the nature of the donor star suggested that V390 Sco is an S-type symbiotic star, likely hosting a less evolved, semiregularly pulsating giant donor, but not a Mira variable.

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.