Abstract We propose that the recently discovered hypersoft X-ray sources can be explained by accretion onto a binary black hole (BH) in a triple system. For BH masses ∼15 M ⊙ , the orbital separation of the internal binary might be ∼0.01 au. If the donor provides ≳10 −8 M ⊙ yr −1 , then the circumbinary disk can explain the observed properties of the most luminous supersoft sources.

Abstract We present high-cadence photometric observations of the Type Ibn supernova (SN) 2022ablq at 60 Mpc, which exploded at an angular separation of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0</mml:mn> <mml:mover accent="true"> <mml:mrow> <mml:mi>.</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>″</mml:mi> </mml:mrow> </mml:mover> <mml:mn>36</mml:mn> </mml:math> from the nucleus of its host galaxy MRK 0762. Following the initial classification, we initiated an intensive monitoring campaign using the 16 inch Schmidt telescope in Algeria, acquiring CCD images in the SDSS- g , r , and i bands. Our light curves provide a dense coverage of the flux evolution from −5 to +54 days with respect to the epoch of g -band maximum ( m peak = 15.20 ± 0.02 mag at MJD = 59914.08), in agreement with previously published analyses.

Abstract Background stars observed through a circumstellar disk provide valuable benchmarks for investigating the disk’s extinction properties. The HD 163296 system is an excellent case study due to its large disk, the clearly visible extinction effects in JWST/NIRCam data, and the presence of numerous background sources within or around its disk. We present the measured contrasts and astrometry of sources surrounding HD 163296 from Cycle 1 JWST/NIRCam coronagraphic observations, which will serve as a useful reference for future studies of the disk’s extinction characteristics.

Abstract Linking low and high-mass star formation is a key goal in star formation theory. Building on the shared framework of inside-out collapse and turbulent core models, forming high-mass sources requires accreting 100–1000× faster than for low-mass stars, for a similar 10 5 yr age. Because high-mass stars quickly disrupt their environments, we focus on intermediate-mass protostars, expected to accrete 10–100× faster while remaining less disruptive. To better probe environment, we focus on Class 0 protostars. First, with the standard assumption of a 0.5 M ⊙ central protostar, we determine infall rates for Class 0 sources from the Herschel Orion Protostar Survey to show a positive correlation between protostellar luminosity and mass infall rate. We then relax this assumption using luminosity as a protostar mass proxy, based on recent studies, to demonstrate that this correlation increases, with intermediate-mass protostars showing 10–40× higher infall rates compared with low-mass stars, consistent with theoretical predictions.

Abstract In mass-transferring binary star systems, classical theories show orbital expansion when q = M donor / M accretor &lt; 1. However, these predictions rely on angular momentum conservation. I show that a ballistic prescription, where transferred mass δm carries the donor’s instantaneous velocity, exhibits linear momentum conservation but implies a systematic loss of orbital angular momentum corresponding to an effective external torque. Specifically, the fractional loss of orbital angular momentum yields L f / L i = 1 − f , i.e., fractional angular momentum loss equals fractional mass transferred.

Abstract We have combined Wide-field Infrared Survey Explorer (WISE) and NEOWISE science exposures spanning from 2010 January through 2024 July to create the deepest ever full-sky maps at 3.4 μ m (W1) and 4.6 μ m (W2). These maps, which we publicly release, are based on ∼11.5 yr of WISE and NEOWISE observations in each of these two bands. As our new all-sky set of full-depth unWISE coadds uniformly incorporates observations from the entirety of the WISE and NEOWISE missions, it represents a valuable legacy dataset for Galactic and extragalactic astronomy in the infrared.

Abstract In the seventeen Cycles 8–24 the first new-cycle sunspot group is tabulated for the first time in each solar hemisphere (thirty-four groups). This allows the determination of the central-value of two parameters of the sunspot-cycle start, as a hemispheric average, since the cycle’s discovery two hundred years ago: first emergence epoch and latitude. The tabulation uses the state-of-the-art cycle-separation data obtained by R. Leussu et al. As a median over the seventeen cycles, the first group is found to have emerged 1.4 yr before sunspot minimum. Its median unsigned latitude is 27 15, lower than in an earlier estimate by A. P. Kramynin &amp; F. A. Mikhalina based on only thirteen groups. This initial median latitude is similar to the ≈27 0 group latitude found by other authors at sunspot minimum epoch. If reproduced, this finding could result in a new observational constraint on solar-dynamo models.

Abstract Dust in elliptical galaxy cores provides insights into the interstellar medium and galactic evolution. I present an automated pipeline analyzing archived Hubble Space Telescope WFPC2 and ACS images to detect and measure dust masses in early-type galaxies. Using iterative unsharp masking with Gaussian smoothing to reconstruct dust-free galaxy models, I derive dust surface densities and estimate total masses from extinction maps using a thin-screen approximation and dust mass absorption coefficient κ λ = 0.77. This automated method enables consistent application to large samples, providing a framework for future large-scale studies.

Abstract The Microlensing Observations in Astrophysics (MOA) collaboration is an international research project that uses gravitational microlensing for the discovery of exoplanets. MOA was initiated in the late 1990s and primarily involves institutions from Japan and New Zealand. The collaboration’s observation site is the Mount John Observatory in New Zealand. We present here an overview of the MOA collaboration data archive, in terms of the monthly and annual number of images taken towards the MOA fields in the Galactic bulge and Magellanic Cloud regions, exposure times, the time between observations, and the monthly altitude distribution of observations (Reasonable requests for MOA data will be considered by the MOA collaboration. Primary contacts for data requests are Preeti Cowan (preeti.cowan@auckland.ac.nz) and Nicholas Rattenbury (n.rattenbury@auckland.ac.nz)).

Abstract We report observations of main-belt asteroid 2025 VZ 8 using multiple telescopes from UT 2025 November 24 to UT 2025 December 23 that confirm the presence of visible comet-like activity. These observations were motivated by online reports that an abrupt brightening event may have led to the object’s discovery on UT 2025 November 9. In all observations reported here, the object displays a tapered tail approximately 3″ long aligned with the antisolar direction. The object has an asteroidal Tisserand parameter value with respect to Jupiter ( T J = 3.371), and is thus considered an active asteroid. We measure an average apparent r ′ -band magnitude of m r ∼ 21.6 mag over the reported observing period. Due to the sudden appearance of activity far from perihelion, we suggest that the activity is more likely due to an impact or rotational destabilization, rather than sublimation.