Thüringer Landessternwarte Tautenburg

Robotic and autonomous observatories are critical for modern time-domain and high-cadence astronomical surveys. The operation of these facilities requires complex software coordination to manage hardware, schedule observations, and ensure safety. However, existing observatory control software are often proprietary and platform-locked or require complex message-brokering infrastructure. Here we present Astra (Automated Survey observaTory Robotised with Alpaca): an open-source, cross-platform Python system for the sustained, fully autonomous operation of astronomical observatories, requiring no external message-broker infrastructure. Astra controls observatory hardware via the ASCOM Alpaca protocol, and executes prescheduled observatory actions under continuous safety supervision. Its multi-device actions include plate-solve-based pointing correction with a local Gaia–2MASS catalogue fallback, PID-controlled autoguiding, and autofocus. A FastAPI web service provides a browser UI, REST and WebSocket APIs for real-time status, image previews, and SQLite-backed telemetry and logs. Astra has run in fully unattended production since January 2024, scaling to six telescopes across three facilities: the SPECULOOS-South network (4 × 1 m class, Chile), SAINT-EX (1 m class, Mexico), and the ETH Observatory (0.5 m class, Switzerland), with no schedule aborts attributable to Astra software. Across the SPECULOOS-South network, it achieves sub-arcsecond autoguiding (0.11 median pointing scatter) and plate-solve failure rates below 1% on three of the four telescopes (3% on the narrowest-field unit), demonstrating that an open, standards-based software stack can meet the reliability demands of production survey astronomy.

Owing to hot and inflated envelopes that facilitate atmospheric studies, ultrahot Jupiters (UHJs) have attracted much attention. Significant progress has been achieved, from enlarging the sample size to broadening the studies to encompass diverse stellar types and ages. Here, we present a transmission spectroscopy study of HAT-P-70b, a UHJ orbiting a young A-type star, through high-resolution observations with CARMENES at the 3.5 m Calar Alto telescope. By using the line-by-line technique, we confirm the previous detections of H α , Na i , and Ca ii , report a new tentative detection of K i , and impose an upper limit on the He triplet absorption. Through cross-correlation analysis, we identify the Ca ii and Fe i absorptions, both blueshifted by approximately 5 km s ^−1 , indicating a day-to-night side atmospheric wind. Additionally, we find a new tentative detection of K i . We do not see any significant atmospheric molecular signal in the near-infrared data. Putting HAT-P-70b in the context of UHJs from the literature, it turns out that (1) H α absorption is more common on gas giants orbiting stars younger than 1 Gyr, with a relative detection probability of P _Age<1 Gyr (H α )/ P _Age≥1 Gyr (H α ) ∼ 3; (2) any UHJ is likely to exhibit Fe i absorption if it has Ca ii .

Context. The interstellar scintillation observed in radio pulsars arises from interference between electromagnetic waves scattered by electron density fluctuations in the turbulent interstellar plasma, providing a critical tool for probing the small-scale structure of the ionized interstellar medium and the pulsar system itself. Aims. The primary aim of this work is to study long-term scintillation variations for a bright and nearby pulsar, PSR J0814+7429, carried out from September 2013 to September 2023 with the LOw-Frequency ARray (LOFAR) High Band Antennae in the frequency range 120-170 MHz. Methods. We derived the basic scintillation parameters, scintillation bandwidth (Δνd), and scintillation timescale (Δτd) from the twodimensional (2D) auto-covariance function of the dynamic spectra that are a 2D matrix of pulse intensity as a function of time and frequency. Results. We present a long-term monitoring study of Δνd and Δτd for PSR J0814+7429, which shows a strong annual variation in the time series of the Δτd. From our modeling of the annual variations of scintillation velocities, the scattering screen is anisotropic and located at 0.23 ± 0.02 kpc from the Earth, likely corresponding to the boundary of the Local Bubble.

We present a quantitative spectroscopic and kinematic analysis of a volume-complete sample of hot subluminous stars within 500 pc of the Sun, assembled using accurate parallax measurements from the Gaia space mission Data Release 3 (DR3). In total, 3226 spectra of 253 hot subdwarf stars were analysed to derive atmospheric parameters (Teff, log g, and helium abundance) and radial velocities. Spectral energy distributions (SEDs) with Gaia parallaxes were used to measure stellar radii, luminosities, and masses. The derived atmospheric parameters reveal a consistent alignment between sdB and sdO stars in the Kiel diagram when compared to theoretical evolutionary models. Notably, we find a substantial population (about 10%) of hot subdwarfs located below the 0.45 M⊙ zero-age extreme horizontal branch (EHB) in both the Kiel and Hertzsprung-Russell diagrams (HRDs), which likely originate from intermediate-mass progenitors (1.8–8 M⊙). The overall mass distribution peaks at 0.48−0.10+0.14 M⊙, while hot subdwarfs below the EHB peak at 0.43−0.09+0.11 M⊙, supporting a scenario of non- or semi-degenerate helium ignition for these objects characteristic of intermediate-mass stars. Interpolation of EHB and post-EHB tracks yields theoretical mass distributions consistent with our estimates based on SED and parallax. By assuming a mass range between 0.40 and 0.50 M⊙ during the interpolation, we further find that the post-EHB birthrate in our sample is 2–3 times higher than the EHB birthrate, which may suggest overestimated EHB lifetimes in theoretical tracks or contamination from other formation and evolutionary channels. Our kinematic analysis shows that 86 ± 2% of the stars belong to the Galactic thin disk, with 13 ± 1% and 1 ± 1% associated with the thick disk and halo, respectively. The below-EHB population is exclusively found in the thin disk, the only Galactic population young enough to harbour intermediate-mass stars. The below-EHB population seems to be absent in other large samples, which generally include more thick disk and halo members. These findings suggest that non-degenerate formation channels may play a more prominent role in the Galactic disk than previously thought.

The mechanical feedback from the central active galactic nuclei (AGNs) can be crucial for balancing the radiative cooling of the intracluster medium (ICM) at the cluster centre. We aim to understand the relationship between the power of AGN feedback and the cooling of gas in the centres of galaxy clusters by correlating the radio properties of the brightest cluster galaxies (BCGs) with the X-ray properties of their host clusters. We used the catalogues from the first SRG/eROSITA All-Sky Survey (eRASS1) along with radio observations from the Australian SKA Pathfinder (ASKAP). In total, we identified 134 radio sources associated with BCGs of the 151 eRASS1 clusters located in the PS1, PS2, and SWAG-X ASKAP fields. Non-detections were treated as upper limits. We correlated the radio properties of the BCGs (radio luminosity, largest linear size/LLS, and BCG offset from the cluster centre) with the integrated X-ray luminosity of the host clusters. We utilised the concentration parameter, $c_{R_{500}}$ , to categorise the clusters into cool cores (CCs) and non-cool cores (NCCs). By combining $c_{R_{500}}$ with the BCG offset, we assessed the dynamical states of the clusters in our sample. Furthermore, we analysed the correlation between radio mechanical power and X-ray luminosity within the CC subsample. We observe a potential positive trend between LLS and BCG offset, which may hint at an environmental influence on the morphology of central radio sources. We find a weak trend suggesting that more luminous central radio galaxies are found in clusters with higher X-ray luminosity. Additionally, there is a positive but highly scattered relationship between the mechanical luminosity of AGN jets and the X-ray cooling luminosity within the CC subsample. This finding is supported by bootstrap resampling and flux-flux analyses. The correlation observed in our CC subsample indicates that AGN feedback is ineffective in high-luminosity (high-mass) clusters. At a cooling luminosity of $L_{\mathrm{X},\,r} \lt \mathrm{R}_{\mathrm{cool}}\approx 5.50\times10^{43}\,\mathrm{erg\,s^{-1}}$ , on average, AGN feedback appears to contribute only about $13\%-22\%$ of the energy needed to offset the radiative losses in the ICM.