The Crimean Astrophysical Observatory (CrAO, obs. code: 095) is located at Nauchnij research campus, near the Central Crimean city of Bakhchysarai, on the Crimean peninsula. CrAO is often called simply by its location and campus name, Crimea–Nauchnij, still ranks among the worldwide most prolific discovery sites for minor planets.CrAO has also been publishing the Bulletin of the Crimean Astrophysical Observatory since 1947, in English since 1977. The observatory facilities (IAU code 095) are located on territory of settlement of Nauchny since the mid-1950s; before that, they were further south, near Simeiz. The latter facilities still see some use, and are referred to as the Crimean Astrophysical Observatory–Simeiz (IAU code 094).
Earthquakes are among the most devastating geological hazards, causing extensive fatalities, infrastructure damage, and environmental disruption worldwide. Despite significant research efforts, near real-time forecasting remains a complex challenge. This study identifies short-term precursors for the February 6, 2023, earthquakes in Turkey (magnitudes 7.8 and 7.5) using data from the INTERMAGNET network. By analyzing geomagnetic field variations and Kp indices, regions of pronounced topological similarity in magnetic field curves were detected at least 150 h, and then in the form of quasi-harmonic fluctuations 5–6 h and 25–30 min before the earthquakes. These findings highlight critical phenomena during the “final preparation” phase of seismic events, contributing to the understanding of earthquake precursors.
Context. Studies of magnetospheric accretion and magnetic field topology in T Tauri stars have advanced over the years, but their applications to fully convective, very-low-mass T Tauri stars remain relatively unexplored. Aims. We aim to analyze the circumstellar environment of the very-low-mass dipper-like star JH 223 by investigating the accretion process and characterizing its large-scale magnetic field topology. Methods. We analyzed the photometric variability of JH 223 using observations from multiple telescopes, including K2, TESS, and LCOGT across different epochs. Additionally, we used Gemini/GRACES spectroscopic and CFHT/SPIRou spectropolarimetric data to investigate the star-disk interaction and to characterize the large-scale stellar magnetic field using Zeeman-Doppler imaging. Results. JH 223 is a fully convective classical T Tauri star with an age of about 3 Myr and a mass of 0.4 M ⊙ . The large-scale surface magnetic field is predominantly poloidal, with a 250 G dipolar component. The dipole field strength and the mass accretion rate indicate that the disk gas truncation radius is located near the corotation radius (6 ± 1 R ★ ). The star-disk interaction, combined with the inclined dipole, generates accretion columns that warp the inner disk. As the star rotates, this warp periodically obscures the stellar surface every 3.31 days, producing the dipper light curves. The same period is also detected in variations of the radial velocity and the longitudinal magnetic field. The accretion columns, traced by strong redshifted absorption components in H α and He I 1083nm, are associated with the inner disk warp, as they occur around the same rotational phase. The accretion process in JH 223 is dynamic, transitioning from an unstable to a stable regime over a few weeks, consistent with predictions from magnetohydrodynamic simulations of the star-disk interaction. Conclusions. Results from multi-technique observations suggest that the magnetospheric accretion model remains valid for fully convective very-low-mass young stars.
The photometric VR_cI_c observations of CW Tau, V773 Tau, FM Tau, FO Tau, CIDA 2, and LkCa 4 in December 2024–November 2025 are described and analyzed. The brightnesses and colors of two potential comparison stars are determined. The rotational modulation of the brightness in LkCa 4 and V773 Tau is confirmed. It is shown that the age of the components FO Tau A and FO Tau B is ∼2.5 Myr, while the age of V773 Tau Aa and V773 Tau Ab is ∼2.3 and ∼3.7 Myr, respectively. The problems of determining the brightnesses and colors of the quiet photosphere in young stars exhibiting a significant photometric variability due to the presence of extended cool photospheric spots, variable circumstellar extinction, and unstable accretion are discussed. The basic physical parameters of the single stars in our sample are determined and discussed. It is noted that the age of FM Tau (9.7–11.2 Myr) determined by taking into account the photometric data and the dynamical mass differs significantly from the mean age of the remaining stars in our sample (2.76 Myr).
Context. Studies of magnetospheric accretion and magnetic field topology in T Tauri stars have advanced over the years, but their applications to fully convective, very-low-mass T Tauri stars remain relatively unexplored. Aims. We aim to analyze the circumstellar environment of the very-low-mass dipper-like star JH 223 by investigating the accretion process and characterizing its large-scale magnetic field topology. Methods. We analyzed the photometric variability of JH 223 using observations from multiple telescopes, including K2, TESS, and LCOGT across different epochs. Additionally, we used Gemini/GRACES spectroscopic and CFHT/SPIRou spectropolarimetric data to investigate the star-disk interaction and to characterize the large-scale stellar magnetic field using Zeeman-Doppler imaging. Results. JH 223 is a fully convective classical T Tauri star with an age of about 3 Myr and a mass of 0.4 M-circle dot. The large-scale surface magnetic field is predominantly poloidal, with a 250 G dipolar component. The dipole field strength and the mass accretion rate indicate that the disk gas truncation radius is located near the corotation radius (6 +/- 1 R-star). The star-disk interaction, combined with the inclined dipole, generates accretion columns that warp the inner disk. As the star rotates, this warp periodically obscures the stellar surface every 3.31 days, producing the dipper light curves. The same period is also detected in variations of the radial velocity and the longitudinal magnetic field. The accretion columns, traced by strong redshifted absorption components in H alpha and He I 1083nm, are associated with the inner disk warp, as they occur around the same rotational phase. The accretion process in JH 223 is dynamic, transitioning from an unstable to a stable regime over a few weeks, consistent with predictions from magnetohydrodynamic simulations of the star-disk interaction. Conclusions. Results from multi-technique observations suggest that the magnetospheric accretion model remains valid for fully convective very-low-mass young stars.
The phosphorus abundance distribution in field stars as a function of metallicity reveals a complex pattern. The LTE data for [P/Fe] in the low-metallicity range are sparse and scattered around [P/Fe] 0 dex. Near [Fe/H] -2 dex, the relative abundance [P/Fe] increases and reaches a maximum value of around [Fe/H] -1 dex. In this domain, P-rich stars and (super)phosphorus-rich stars are observed; the [P/Fe] value can exceed 1 dex. Until now, no attempts have been made to study the NLTE effects on the ultraviolet and infrared phosphorus lines in spectra of cool stars to test the robustness of the observed LTE phosphorus abundance distribution. We developed an atomic model of P I that can be used to analyze phosphorus lines in the spectra of cool dwarfs and giants in the NLTE approximation. The model was tested using the solar flux and intensity spectra, as well as the spectra of Procyon and sigma Boo. Profiles of 14 phosphorus lines in the infrared regions and equivalent widths were analyzed. Our NLTE phosphorus abundance in the Sun is (P/H)=5.35+/-0.04 dex. Using our NLTE model, we selected 12 ultraviolet and infrared phosphorus lines and calculated a grid of NLTE corrections for the following parameter ranges: Teff from 4000 to 6750 K, step 250 K; log g from 1 to 5 dex, step 1 dex; and Vt = 2 km/s, [Fe/H] from -3 to +0.5 dex, step 0.5 dex. The NLTE corrections were calculated for phosphorus abundance ratios of [P/Fe]=-0.4, 0.0, +0.4 dex. For the Sun, the NLTE correction is -0.08 dex. The grid of the NLTE corrections, as well as the direct line profile synthesis, were used to refine the literature data on the phosphorus abundance in metal-poor, intermediate-deficient, and solar-metallicity stars. NLTE corrections do not qualitatively alter the overall phosphorus abundance distribution over a wide metallicity range, and do not change the characteristic pattern of phosphorus-rich stars.
