Abstract Geostationary motion provides a repeating observer baseline that can encode target range in coronagraph images. We apply this to GOES-19/CCOR-1 by registering each frame to field stars and fitting the fixed-phase sidereal-day parallax jointly with smooth sky motion. Thirteen known-distance tracks of planets, asteroids, and comets spanning 0.49–20.5 au yield a median absolute fractional range error of 2.4%; the smallest recovered semiamplitude is 2 . ″ 6 (0.13 pixel). A field-star null gives 0 . ″ 8, while independently hand-clicked positions reproduce the trend shown by results from automated linker positions. The inferred range also resolves the line-of-sight geometry, correctly placing 3I/ATLAS beyond the Sun and C/2025 R3 between the observer and the Sun. A geostationary coronagraph therefore provides orbit-free line-of-sight information for near-Sun objects inaccessible to ground-based diurnal-parallax programs.
Abstract I report a candidate photometric period for the main-belt asteroid (2412) Wil, which has no previously published rotation period. The value is derived solely from publicly available sparse photometry. The Lomb–Scargle periodogram of Zwicky Transient Facility (ZTF) alert photometry from the 2021 apparition peaks at 11.863 ± 0.016 hr; the periodogram of the fully independent Gaia DR3 photometry of the same object, computed on the same period grid, has its global maximum 0.002 hr away, at 11.861 hr. The peak-to-peak amplitude on the P fold is 0.37 ± 0.03 mag. A test with pre-specified thresholds for a difference between the halves of the fold on twice the period does not meet the acceptance criterion, and its outcome is itself sensitive to the phase-curve model, so the rotation period is either 11.863 hr or twice that value, 23.726 hr. Dense follow-up photometry is encouraged.
Abstract I present a discovery of possible white dwarf companion to HD 31878. It was detected only by Gaia, as it is located very close to bright star ( ∼ 4 . ″ 2 ). Gaia DR3 parallax and proper motion are nearly identical for these two stars. Color magnitude diagram (CMD) suggests that it is wide binary ( P orb ∼ 23,000 yr) consisting a main sequence primary and white dwarf secondary.
Abstract Epsilon Eridani ( ϵ Eri) is considered to be the nearest young-Sun-like star. Observing stellar flares on ϵ Eri provides insights into the radiation experienced by an early Earth. Multiwavelength observations of these events are necessary to truly understand them, yet these datasets remain rare partly due to the difficulty of multiwavelength campaigns. Here, we report on 10 hr of 8–12 GHz data from the Karl G. Jansky Very Large Array (VLA) during which no requested multiwavelength observations were collected and no significant flares occurred. However, ϵ Eri is detected in quiescence and is fairly consistent with previous observations, having a flux density around 47 μ Jy.
Abstract The precessing jets of the microquasar SS 433 have a speed ∼0.26 c . Variations in the speed with which matter is ejected are associated with changes in delivery from the Companion to the (slaved) accretion disk of the black hole; in the optical jets, speeds share the orbital period of 13.08 days. This period has a subharmonic, the most prominent aspect, together with implausibly spaced sidebands, here discussed and previously overlooked. These involve beats with subharmonics of the precession. The relationship between the response of the jet speed and the driving periodic motions of the orbit and precession must be nonlinear.
Abstract Nu Pictoris is a nearby Am star which was found to be a P ≃ 450 days astrometric binary from Hipparcos intermediate astrometric data (IAD). Here we report on a VLTI/GRAVITY observation in which we detected a companion to ν Pic at a projected separation ρ = 3.35 mas ↔ 0.17 au. The isochrone masses are M A ≃ 1.7 M ⊙ and M B ≃ 0.8 M ⊙ and coronal activity in the detected K dwarf companion can explain the hard X-ray emission in eROSITA as well as the flare in TESS observations of ν Pic. The fact that our measured projected separation is much smaller than the expected semimajor axis a = 31.2 mas is likely due to the orbit being close to edge on, although we cannot completely exclude the possibility that ν Pic is a triple system with a faint M dwarf or white dwarf outer companion.
Abstract This paper will consider the detection and study of transients on a telescope MASTER-OAFA using the example of objects MASTER OT J130509.66-415546.1, MASTER OT J121326.51-314615.8 and MASTER OT J121307.81-302546.8.
Abstract We report the identification of 21 previously unrecognized superfast rotators in early Rubin Observatory Legacy Survey of Space and Time (LSST) observations contained in the 2026 April and June Asteroid Institute data releases. Rotation periods were independently derived using high-order Fourier and multiband Lomb–Scargle analyses, providing mutually consistent solutions within our adopted reliability criteria. None of these objects has previously published rotation periods or color measurements, and six receive their first taxonomic classifications. These results demonstrate the capability of Rubin’s early multiband observations to efficiently discover and physically characterize previously unknown superfast rotators.
Finch et al (2002) derived relations for the summed absolute magnifications of quadruply lensed images that vary inversely with flattening in two alternative isothermal gravitational potential models. However, they did not elaborate on the selection effects this "flatter-fainter” relation induces in actual lensed systems. We test the relation against the Luhtaru et al (2021) sample of 39 quadruply lensed quasars (38 of which we model successfully), using predicted rather than observed magnifications to avoid the complication of microlensing. We found that the summed predicted magnification decreases by a factor of ten over the observed range of flattening.
Abstract SN 2019ehk had a serendipitous spectra from the Very Large Telescope (VLT)/Multi Unit Spectroscopic Explorer (MUSE) taken about 19 hr prior to explosion. MUSE reobserved that location 330 days post explosion, allowing for comparison of pre- and post-explosion data. The world coordinate systems (WCS) in both files are slightly misaligned compared to external references, such as Gaia. When evaluating pre- or post-imaging of a transient, it is vital to have an accurate location relative to external sources. We correct the WCS to ensure that the brightest spaxel of the galaxy in the MUSE data matching the R.A. and decl. of the galaxy in Gaia. These shifts are on the order of 1–5 pixels or <1 ″ .
TeV-emitting BL Lacertae (BL Lac) blazars have important implications for the study of jet phenomenology, particle acceleration, and ultra high-energy cosmic ray production. They also allow for indirect studies of the extragalactic background light, cosmic magnetic fields, and axion-like particles. The upcoming Cherenkov Telescope Array (CTA), a ground-based gamma-ray observatory, will expand the observed TeV-emitting BL Lac population and enhance the aforementioned fields of study. However, reliable redshifts are crucial for planning and interpreting observations with CTA and only about 50
The 96 Glyphs Mural at Ek’ Balam (Star-Jaguar), in the Yucatán Peninsula of Mexico, records the arrival of Chak Jutuuw Chan Ek’ on 770 April 7 and the enthronement of Ukit Kan Le’k Tok’ 49 days later, on 770 May 26. Chinese historical records dated to the same day report comet C/770 K1 with a tail length of about 30 ∘ –50 ∘ . Hasegawa’s reconstructed orbit is projected onto the local sky at Ek’ Balam. On May 26, the cometary head reaches altitudes of 3 . ° 4 at 04:30, 8 . ° 8 at 05:00, and 11 . ° 5 at sunrise near 05:16 local solar time. The reported tail length and the low relief of northern Yucatán favor naked-eye visibility. This coincidence between the enthronement and the Chinese records merits further epigraphic and astronomical investigation to establish or reject a historical connection.
Binary systems with black hole or neutron star companions are often associated with lithium enhancement. Gaia NS1, a recently discovered neutron-star binary with a lithium-enhanced main-sequence companion, demonstrates the potential of lithium as a signpost for identifying compact object binaries in existing spectroscopic surveys. In particular, we aim to use lithium as a signpost to find compact object binaries similar to Gaia NS1 in the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) Medium Resolution Survey (MRS). From LAMOST MRS, we selected 4441 metal-poor main-sequence stars like Gaia NS1, measured the Li 6707 Å equivalent width, and then identified a sample of 33 stars with strong Li absorption. We used radial velocity variation and astrometric binarity signatures from Gaia, narrowing the sample to 3 candidates. We identified one of these candidates as an eclipsing binary and demonstrated that massive companions for the other two are unlikely via follow-up spectroscopy.
We present the discovery of Aquarius IV (Rubin J2201-0234) – the first ultra-faint Milky Way satellite to be identified using data from the Vera C. Rubin Observatory. This system was detected at ∼8σ significance using Rubin Early Data Preview 2 (EDP2) photometry and independently confirmed at ∼6σ significance in archival Dark Energy Camera imaging. Jointly fitting its morphology and distance, we find that Aquarius IV is a low-luminosity (M_V=-1.9^+0.6_-1.0), compact (r_1/2 = 19^+4_-6 pc; r_h = 0.60^+0.14_-0.17 arcmin) stellar system in the outer Galactic halo (D_⊙ = 109^+6_-8 kpc). Its stellar population is consistent with an ancient, metal-poor stellar isochrone (τ= 13 Gyr, Z=0.0001). These properties closely resemble those of the smallest and faintest confirmed ultra-faint dwarf galaxies, though a globular cluster classification is not ruled out. Given the small number of detected member stars in Rubin EDP2, deeper imaging and spectroscopy will be critical for determining the properties and classification of Aquarius IV at higher confidence.
Abstract Shock fronts produced in galaxy cluster mergers are commonly used to infer the dynamical conditions of the collision, including the relative velocity of the clusters. In this work we investigate how the initial infall velocity affects the strength of merger shocks in unequal-mass systems. We perform idealized hydrodynamical simulations of cluster mergers with a mass ratio of 1:10 and initial approach velocities ranging from 0 to 3000 km s −1 . The Mach number and temperature of the shock fronts are measured after core passage during the outgoing phase of the merger. We find that both quantities vary only weakly across the explored velocity range, with shocks consistently exhibiting –3 and temperatures of ∼7–9 keV. These results indicate that, for highly unequal-mass mergers, shock strength is not very sensitive to the initial approach velocity.
Abstract SD + was tentatively detected via the N J = 1 2 –0 1 transition at 271.406 GHz toward the Orion Bar using the IRAM 30 m telescope. This ion appeared as a line of T mb = 11 ± 4 mK with a width of 1.8 ± 0.7 km s −1 at the same velocity as the clear detection of another sulfur-bearing cation, HCS + . This line suggests a deuteration ratio of the protonated atom, SD + /SH + , as 0.4%–0.5%, which is clearly lower than the DCN/HCN ratio of 1.1% in the nearby clump. Though the deuteration ratio for SH + is lower than HCN, they are broadly compatible. Furthermore, CH 2 NH was detected for the first time in a photodissociation region. Its column density is derived to be 9.7 × 10 12 cm −2 when assuming an excitation temperature of 9 K.
Abstract I present PlanetFlow, an open-source Python application with a graphical user interface for automated end-to-end post-processing of ground-based planetary video observations. The standard workflow for high-resolution planetary imaging—planet detection, lucky stacking, quality assessment, rotation correction, wavelet sharpening, and multi-channel compositing—has until now required chaining several Windows-only programs with manual file transfer at each stage. PlanetFlow integrates this workflow into a single application running natively on both Linux and Windows, executing all stages from raw SER video to final RGB composite in a single session. Key design choices include Fourier-domain quality-weighted stacking, Gaussian kernel regression for continuous warp-field interpolation, and automatic pole-angle retrieval from the NASA JPL Horizons service for spherical de-rotation. The pipeline supports both monochrome filter-wheel and color Bayer-sensor cameras. PlanetFlow is freely available at Zenodo and GitHub under the MIT license.
Abstract I revisit the contradictory claims regarding the detection of low-frequency extra modes in the RR Lyrae star HH Puppis. A Research Note by T. Love noted that the star shows no extra signals in the Transiting Exoplanets Survey Satellite (TESS) observations. In a response, M. Chadid attributed this to the limitations of the TESS mission over their longer dataset collected with the PAIX instrument they used. Here I show that some of the capabilities of TESS have been underestimated, and the claims made could be verified with a more detailed analysis (and public release) of the PAIX data.
Abstract We update the predictions for Vera C. Rubin Observatory Legacy Survey of Space and Time measurements of ultracool dwarf parallaxes in light of changes in the recommended survey strategy and performance. Despite numerous changes, the predicted volume probed for the 2025 recommended strategy (OpSim V5.0) was within a few percent of the 2022 (OpSim V1.7) results over ten years. Increasing predicted survey downtime (OpSim V5.3) to more realistic values, however, results in volumes about 10% lower. We draw attention to how the rolling cadence strategy affects parallax performance in parts of the sky over the first two years. Overall, Rubin is predicted to significantly increase the numbers of L and T dwarfs with parallaxes over current samples, enabling studies of very-low-mass stars and brown dwarfs.
Abstract Classical Be stars are rapidly rotating B stars that eject material into an equatorial gaseous disk. The disk can be observed through spectroscopy of emission lines and infrared excesses, where polarimetry or interferometry can reveal the orientation of the disk. The mechanisms that lead to stellar mass ejection are still unknown, so the discovery of periodic disk ejections is important to predict when to observe certain Be stars and also reveals that the underlying mass ejection mechanism can be periodic, which is an important clue to understand the physical mechanisms involved. Previously, the classical Be star HD 6226 was found to have a periodic disk behavior from four years of spectroscopy. Here we report on a time-series analysis of ∼20 yr of H α and H β spectroscopy and confirm the quasi-periodic behavior of the disk growth and dissipation.
