https://astro.theoj.org/ The Open Journal of Astrophysics is an arXiv overlay journal providing open access to peer-reviewed research in astrophysics and cosmology. en Fri, 12 Jun 2026 06:34:00 +0000 This article presents observations of the third Interstellar Object, 3I/ATLAS, providing early sub-mm constraints on its activity. The findings suggest a steeper production rate slope than typical Solar System comets. https://doi.org/10.33232/001c.163250 https://astro.theoj.org/article/163250-jcmt-constraints-on-the-early-time-hcn-and-co-emission-and-hcn-temporal-evolution-of-3i-atlas Thu, 11 Jun 2026 07:12:00 +0000 The X-SORTER program identifies merging galaxy clusters to study dark matter interactions, using optical indicators and X-ray observations. This method efficiently identifies active clusters suitable for detailed dark matter studies. https://doi.org/10.33232/001c.163212 https://astro.theoj.org/article/163212-x-sorter-x-ray-survey-of-merging-clusters-in-redmapper-x-ray-and-spectroscopic-characterization-of-12-optically-selected-galaxy-cluster-merger-cand Thu, 11 Jun 2026 06:58:00 +0000 This article explores how galaxy mergers, like the Milky Way-Large Magellanic Cloud merger, significantly alter the properties and structures of stellar streams, challenging the recovery of their initial orbits. https://doi.org/10.33232/001c.163211 https://astro.theoj.org/article/163211-dancing-streams-in-merging-halos-stellar-streams-in-a-mw-lmc-like-merger Thu, 04 Jun 2026 11:06:00 +0000 The "Reduced Speed of Light" approximation in cosmological simulations can lead to photon non-conservation, and while some missing photons can be counted, adding them back is challenging. https://doi.org/10.33232/001c.162879 https://astro.theoj.org/article/162879-photon-non-conservation-in-the-reduced-speed-of-light-approximation-and-how-to-almost-fix-it Wed, 03 Jun 2026 05:08:00 +0000 The thermal Sunyaev-Zel'dovich effect and constrained simulations are used to analyze the thermal pressure of ionized gas in galaxy clusters and produce a set of digital twins for cosmological study https://doi.org/10.33232/001c.162811 https://astro.theoj.org/article/162811-validating-digital-twins-of-the-local-universe-with-the-thermal-sunyaev-zel-dovich-signal Tue, 02 Jun 2026 07:48:00 +0000 A model to understand the role of nozzle shock in the circularization of stellar debris during a tidal disruption event when a star approaches a supermassive black hole (SMBH) https://doi.org/10.33232/001c.162785 https://astro.theoj.org/article/162785-resolving-the-debate-about-nozzle-shocks-in-tidal-disruption-events Tue, 02 Jun 2026 07:27:00 +0000 The study suggests that X-ray transients, similar to tidal disruption events, are produced in eccentric stellar-compact object binaries, with their frequency gradually increasing over time. https://doi.org/10.33232/001c.162784 https://astro.theoj.org/article/162784-transient-x-ray-sources-as-extremely-eccentric-mass-transfer-binaries-with-compact-companions Tue, 02 Jun 2026 07:14:00 +0000 This article explores how uncertainties in binary formation affect the cross-correlation signal between gravitational wave events and galaxy catalogues, finding that time-delay distribution significantly impacts the signal. https://doi.org/10.33232/001c.162783 https://astro.theoj.org/article/162783-the-impact-of-the-formation-channel-on-gravitational-wave-galaxy-cross-correlations Tue, 26 May 2026 06:56:00 +0000 Testing the accuracy of stellar age estimates from recent catalogs, finding that spectroscopic metallicities provide reliable subgiant ages, while photometric ages underestimate uncertainties. Accurate chemical abundance measurements are essential. https://doi.org/10.33232/001c.162534 https://astro.theoj.org/article/162534-how-precisely-can-we-measure-the-ages-of-subgiant-and-giant-stars Tue, 26 May 2026 06:35:00 +0000 This study explores the use of control variates in cosmological simulations, introducing a new 'shifted control variate' that improves precision and enables accurate bispectrum emulators, aiding in cosmology modeling. https://doi.org/10.33232/001c.162533 https://astro.theoj.org/article/162533-control-variates-from-eulerian-and-lagrangian-perturbation-theory-application-to-the-bispectrum