The fifth-generation Sloan Digital Sky Survey (SDSS-V) includes the first large-scale spectroscopic survey of white dwarfs (WDs) in the era of Gaia parallaxes. SDSS-V collects multiple exposures per target, making it ideal for binary detection. We present a search for hydrogen atmosphere (DA) double WD (DWD) binaries in this rich dataset. We quantify radial velocity variations between subexposures to identify binary candidates, and we measure the orbital period for a subset of DWD binary candidates. We find 60 DWD binary candidates, of which 43 are new discoveries, and report tentative periods for 9 of these binaries. From these binary candidates, we derive a Galactic WD binary fraction f _bin,0.4 = 9% for binary separations <0.4 au and the power-law index of the initial separation distribution α = −0.62. Using the simulated binary population, we find that approximately two to five super-Chandrasekhar-mass binaries that merge within a Hubble time are expected in our sample at a 95% confidence interval. We predict that approximately two systems in our sample should be detectable via gravitational waves by the Laser Interferometer Space Antenna (LISA), one of which has already been identified as a LISA verification source. We also estimate a total of about 10,000–20,000 LISA-detectable DWD binaries in the Galaxy. Our catalog of WD+WD binary candidates in SDSS-V is now public and promises to uncover a large number of exciting DWD systems.
We discuss the most recent observations made with the Southern Connecticut Stellar Interferometer, which is a three-station stellar intensity interferometer located on the campus of Southern Connecticut State University, in New Haven, Connecticut. Two different kinds of observations are presented. We first analyze observations of Vega taken in a three-telescope mode. (Previously, the instrument had only two operational stations.) We show that, while the efficiency remains nearly identical to that reported in our last paper, the addition of the third station allows more photon data to be recorded simultaneously, and therefore we can build up the photon-bunching peak in the data stream in fewer hours on sky for an unresolved source. In the second part of the paper, we report our observations to date of the nearby red giant star Arcturus, most of which occurred in the first half of 2025. These show that, as a partially resolved source at the baselines we used, we detect fewer correlations in the photon-bunching peak than for an unresolved source of comparable brightness. Combining the data with speckle imaging observations taken at Apache Point Observatory, we derive a new measurement of Arcturus’ diameter that extends the temporal baseline of interferometric observations of the star and is consistent with previous analyses made by other investigators.
Weywot is the largest satellite of the candidate dwarf planet Quaoar, which also hosts a remarkable ring system located beyond its Roche limit—a configuration that challenges conventional understanding of ring dynamics. In this work, we predicted three stellar occultations by Weywot occurring in 2023 May and June, of which one was successfully observed on 2023 June 22. This multichord event took place over North America, where observers were deployed across the shadow path from Maryland to California. Five positive detections and two near misses allowed us to accurately constrain Weywot’s projected size and shape at the time of the occultation. We constrained the equivalent diameter to be between 116 and 172 km (with 95% confidence) and estimate a geometric albedo between 0.024 and 0.078—substantially lower than that of Quaoar. These results offer new insights into the physical properties of Quaoar’s system and provide valuable constraints for models of its formation and evolution.
Imminent impactors may be detected only a few hours before their impact with Earth, providing a brief opportunity to characterize them before impact. We describe the characterization of imminent impactor 2024 RW _1 , which was discovered by the Catalina Sky Survey on 2024 September 4 at 05:43 UTC, before it entered the atmosphere near the northern Philippines at 16:39 UTC. We observed 2024 RW _1 with the Astrophysical Research Consortium Telescope Imaging Camera on the Apache Point Astrophysical Research Consortium’s 3.5 m telescope on 2024 September 4 at 10:16 UTC. We obtained g , r , i , and z photometry of 2024 RW _1 , yielding color indices of g – r = 0.47 ± 0.04, r – i = 0.13 ± 0.04, i – z = –0.11 ± 0.07, and g – i = 0.60 ± 0.04, corresponding to a spectral slope of 0.67 ± 0.40 %/100 nm. The closest match to an asteroid spectral type is with B-type asteroids from the C complex. We detect variations in the time-series photometry of the asteroid with an amplitude of ∼0.75, and a double-peaked rotation period of ∼1900 s. Assuming a visible albedo of 0.07 ± 0.03, a density of ∼1500 kg m ^−3 , and a calculated absolute magnitude of 30.92 ± 0.05, we estimate that the asteroid has a diameter of 3.3 ± 0.7 m and a total mass of ∼28,000 kg. Comparing our astrometric orbital solutions to NEOMOD3, the most likely source of 2024 RW _1 is the 3:1 main-belt mean-motion resonance (77% probability) followed by the ν _6 resonance (13% probability), consistent with its organic B-type nature.
The Sunspot Solar Observatory Data Archive (SSODA) stores data acquired with the suite of instruments at the Richard B. Dunn Solar Telescope (DST) from February 2018 to the present. The instrumentation at the DST continues to provide high cadence imaging, spectroscopy, and polarimetry of the solar photosphere and chromosphere across a wavelength range from 3500 Å to 11,000 Å. At the time of writing, the archive contains approximately 374 TiB of data across more than 520 observing days (starting on February 1, 2018). These numbers are approximate as the DST remains operational, and is actively adding new data to the archive. The SSODA includes both raw and calibrated data. A subset of the archive contains the results of photospheric and chromospheric spectropolarimetric inversions using the Hazel-2.0 code to obtain maps of magnetic fields, temperatures, and velocity flows. The SSODA represents a unique resource for the investigation of plasma processes throughout the solar atmosphere, the origin of space weather events, and the properties of active regions throughout the rise of Solar Cycle 25.
